Refactor cryptojs includes

 * Adds a build step to the makefile to concatenate the crytojs files.

   This makes upgrading straightforward, without the need to add headers
   to each individual file, leaving the source unmodified. It also means
   that one file needs to be included per page.

 * Adds pbkdf2.
Re-enabled file transfers

 * Uses the otr extra symmetric key as password and filename as
   diversifier to a key derivation function, the result of which is
   split and used as encrypt and mac keys. This was suggested in the
   Least Authority audit to prevent several attacks due to the re-use of
   key and iv when multiples files were sent in the same direction
   without the otr key having rolled over.

 * Also, it was suggested to store the encrypt and mac keys in a named
   structure rather than an array.
as seen in the source code itself, the plugin is released under GNU GPL 3.0. yay. https://github.com/jcobb/basic-jquery-slider/blob/master/js/bjqs-1.3.js
Merge pull request #653 from u451f/licensing

updated license for jquery-basic-slider
Fix #657
Merge pull request #628 from arlolra/ft

Re-enable file transfers
UI fix
Fixes for #628
Fix file transfer after Facebook refactor (#628)
Cleanup
Attempting to make file transfer work over Facebook
Fix #577
Update Ukrainian translation (#331)
Load more Facebook contacts on connect
Mac window size tweaks
Cryptocat 2.2.2

- Encrypted file transfer is now back in Cryptocat after being
temporarily disabled pending review. Note that encrypted file transfer
is not available over the Encrypted Facebook Chat feature.
- Updated Ukrainian translation.
- Small bug fixes.
Improve regex check as suggested by @arlolra

https://github.com/cryptocat/cryptocat/commit/9aef609d3dcc7fd4c20c5e7d53
fdbd76d57eabe7#commitcomment-6650111
Template naming improvement suggested by @arlolra

https://github.com/cryptocat/cryptocat/commit/6adec964fc4181f0c5718ff4e5
ab71fe74c456e5#commitcomment-6650257
Scope file transfer errors
Update CONTRIBUTING.md