Add more prominent distinction between files and directories in jstree view

[jdaguil]

Originally from #41.

Additionally, perhaps listing the folder icons in a different color (like the way ls on a unix machine) could be added as well to further distinguish between files and directories.

[jdaguil]

@johnmhoran I suggest changing the current Glyphicons to FontAwesome icons.

For the directory icon: fa fa-folder
For the file icon: fa fa-file-text-o
For the open directory icon: fa fa-folder-open
For the closed directory icon: fa fa-folder