Fixed the "mixed tabs and spaces" issue

Updates:

1. The plugin correctly inserts any external files needed for the
   testing frameworks (currently, the plugin only knows about the
   "mocha" framework. Others will be added later)
2. It will search for specific tags (position where to place the external
   files) but if those tags don't exist, then it will place the files at
   the bottom of the <head> tag (just before the </head> tag)

ToDo:

1. Have the plugin insert "extra" tags in the <body> tag. The tags are
   used to initialize the frameworks and can be defined by the user.
2. Before inserting the external tags, the plugin should check to see if
   the file is already requested (a simple search should suffice)