ci: remove node 4, loosen node image versions

.circleci/config.yml

@@ -6,7 +6,7 @@ version: 2
 jobs:
   node8:
     docker:
-      - image: circleci/node:8.11
+      - image: circleci/node:8
     working_directory: ~/repo
     steps:
       - checkout
@@ -23,24 +23,7 @@ jobs:
 
   node6:
     docker:
-      - image: circleci/node:6.11.4
-    working_directory: ~/repo
-    steps:
-      - checkout
-      - restore_cache:
-          keys:
-            - v1-dependencies-{{ checksum "package.json" }}
-            - v1-dependencies-
-      - run: yarn install
-      - save_cache:
-          paths:
-            - node_modules
-          key: v1-dependencies-{{ checksum "package.json" }}
-      - run: yarn test
-
-  node4:
-    docker:
-      - image: circleci/node:4.8.4
+      - image: circleci/node:6
     working_directory: ~/repo
     steps:
       - checkout
@@ -57,7 +40,7 @@ jobs:
 
   lint:
     docker:
-      - image: circleci/node:8.11
+      - image: circleci/node:8
     working_directory: ~/repo
     steps:
       - checkout
@@ -74,7 +57,7 @@ jobs:
 
   coveralls:
     docker:
-      - image: circleci/node:8.11
+      - image: circleci/node:8
     working_directory: ~/repo
     steps:
       - checkout

.gitattributes

@@ -1,3 +1,4 @@
 *.js text eol=lf
 *.md text eol=lf
 yarn.lock text eol=lf
+*.yml text eol=lf

README.md

@@ -229,7 +229,7 @@ yarn lint
 
 ## Compatibility
 
-This package is compatible all the way down to Node 4 and IE9. It might be
+This package is compatible all the way down to Node 6 and IE9. It might be
 compatible with older versions of Node/IE, but such guarantees cannot be made.
 
 ## Versioning