Reverse conditionals

In order to avoid the usage of the negation on the conditionals wich
helps to:

- Makes simpler to understand the logic on that block of the code
- Easier to read
- Avoid usage of a negation

lib/vulcan.js

@@ -96,15 +96,15 @@ var Vulcan = function Vulcan(opts) {
   this.inputUrl = String(opts.inputUrl) === opts.inputUrl ? opts.inputUrl : '';
   this.fsResolver = opts.fsResolver;
   this.redirects = Array.isArray(opts.redirects) ? opts.redirects : [];
-  if (!opts.loader) {
+  if (opts.loader) {
+    this.loader = opts.loader;
+  } else {
     this.loader = buildLoader({
       abspath: this.abspath,
       fsResolver: this.fsResolver,
       excludes: this.excludes,
       redirects: this.redirects
     });
-  } else {
-    this.loader = opts.loader;
   }
 };
 
@@ -209,13 +209,13 @@ Vulcan.prototype = {
     this.fixFakeExternalScripts(doc);
     this.pathResolver.acid(doc, tree.href);
     var moveTarget;
-    if (!isMainDoc) {
-      moveTarget = dom5.constructors.fragment();
-    } else {
+    if (isMainDoc) {
       // hide bodies of imports from rendering in main document
       moveTarget = dom5.constructors.element('div');
       dom5.setAttribute(moveTarget, 'hidden', '');
       dom5.setAttribute(moveTarget, 'by-vulcanize', '');
+    } else {
+      moveTarget = dom5.constructors.fragment();
     }
     head.childNodes.filter(this.moveToBodyMatcher).forEach(function(n) {
       this.removeElementAndNewline(n);