refactor(legacy support): use unified component

* uses `in-element-polyfill` and `maybe-in-element` AST transforms to allow to use `in-element` with legacy support back to Ember 1.13 (ember-wormhole based)
* Cleaned up unnecessary legacy components

Closes kybishop#71

BREAKING CHANGE:
Support for Ember <1.13 has been dropped!

.travis.yml

@@ -21,7 +21,6 @@ env:
   matrix:
     # we recommend new addons test the current and previous LTS
     # as well as latest stable release (bonus points to beta/canary)
-    - EMBER_TRY_SCENARIO=ember-1.11
     - EMBER_TRY_SCENARIO=ember-1.13
     - EMBER_TRY_SCENARIO=ember-lts-2.4
     - EMBER_TRY_SCENARIO=ember-lts-2.8

addon/templates/components/ember-popper-targeting-parent.hbs

@@ -1,6 +1,12 @@
 {{unbound _parentFinder}}
 
-{{#if renderInPlace}}
+{{!-- Elements that exist deep within the document tree are given an implicitly lower z-index
+      value than elements that aren't as deep in the tree; this has the effect of hiding our
+      ember-popper behind less-nested elements. Due to the way z-indexing works, we cannot simply
+      add a higher z-index value to our ember-popper. To avoid this issue, we render the element
+      on the document body, giving it the highest default z-index value. --}}
+{{#maybe-in-element _popperContainer renderInPlace}}
+{{!-- Add a wrapper around the yielded block so we have something for the Popper to target --}}
   <div id={{id}} class={{class}} role={{ariaRole}}>
     {{yield (hash
       disableEventListeners=(action 'disableEventListeners')
@@ -9,21 +15,4 @@
       update=(action 'update')
     )}}
   </div>
-{{else}}
-  {{!-- Elements that exist deep within the document tree are given an implicitly lower z-index
-        value than elements that aren't as deep in the tree; this has the effect of hiding our
-        ember-popper behind less-nested elements. Due to the way z-indexing works, we cannot simply
-        add a higher z-index value to our ember-popper. To avoid this issue, we render the element
-        on the document body, giving it the highest default z-index value. --}}
-  {{#-in-element _popperContainer}}
-    {{!-- Add a wrapper around the yielded block so we have something for the Popper to target --}}
-    <div id={{id}} class={{class}} role={{ariaRole}}>
-      {{yield (hash
-        disableEventListeners=(action 'disableEventListeners')
-        enableEventListeners=(action 'enableEventListeners')
-        scheduleUpdate=(action 'scheduleUpdate')
-        update=(action 'update')
-      )}}
-    </div>
-  {{/-in-element}}
-{{/if}}
+{{/maybe-in-element}}

addon/templates/components/ember-popper.hbs

@@ -1,4 +1,10 @@
-{{#if renderInPlace}}
+{{!-- Elements that exist deep within the document tree are given an implicitly lower z-index
+      value than elements that aren't as deep in the tree; this has the effect of hiding our
+      ember-popper behind less-nested elements. Due to the way z-indexing works, we cannot simply
+      add a higher z-index value to our ember-popper. To avoid this issue, we render the element
+      on the document body, giving it the highest default z-index value. --}}
+{{#maybe-in-element _popperContainer renderInPlace}}
+  {{!-- Add a wrapper around the yielded block so we have something for the Popper to target --}}
   <div id={{id}} class={{class}} role={{ariaRole}}>
     {{yield (hash
       disableEventListeners=(action 'disableEventListeners')
@@ -7,21 +13,4 @@
       update=(action 'update')
     )}}
   </div>
-{{else}}
-  {{!-- Elements that exist deep within the document tree are given an implicitly lower z-index
-        value than elements that aren't as deep in the tree; this has the effect of hiding our
-        ember-popper behind less-nested elements. Due to the way z-indexing works, we cannot simply
-        add a higher z-index value to our ember-popper. To avoid this issue, we render the element
-        on the document body, giving it the highest default z-index value. --}}
-  {{#-in-element _popperContainer}}
-    {{!-- Add a wrapper around the yielded block so we have something for the Popper to target --}}
-    <div id={{id}} class={{class}} role={{ariaRole}}>
-      {{yield (hash
-        disableEventListeners=(action 'disableEventListeners')
-        enableEventListeners=(action 'enableEventListeners')
-        scheduleUpdate=(action 'scheduleUpdate')
-        update=(action 'update')
-      )}}
-    </div>
-  {{/-in-element}}
-{{/if}}
+{{/maybe-in-element}}

config/ember-try.js

@@ -11,28 +11,6 @@ module.exports = function() {
     return {
       useYarn: true,
       scenarios: [
-        {
-          name: 'ember-1.11',
-          bower: {
-            dependencies: {
-              'ember': '~1.11.0',
-              'ember-cli-shims': '0.0.6'
-            },
-            resolutions: {
-              'ember': '~1.11.0',
-              'ember-cli-shims': '0.0.6'
-            }
-          },
-          npm: {
-            devDependencies: {
-              'ember-cli-fastboot': null,
-              'ember-cli-shims': null,
-              'ember-native-dom-event-dispatcher': null,
-              'ember-source': null,
-              'fastboot': null
-            }
-          }
-        },
         {
           name: 'ember-1.13',
           bower: {