Fixes/Features in 1.3.8:

* New syntax highlighting using Ace Editor
* Syntax highlighting themes
* Tree/folder structure for saving requests
* No reordering of JSON keys on pretty printing
* Adds text/plain to Content-Type menu
* Uses ARC for memory management
* Should hopefully fix text box display issues on latest OS X versions >= 10.10
* Fixes bug where requests are only saved on exit
* New icon!