Support for IRCCloud's new upload feature

[Dahlgren]

Enables both drag'n'drop and file upload form

[zachlatta]

:+1:

[bemjb]

I created a new build that includes this change: https://github.com/jnordberg/irccloudapp/releases/tag/0.7.5-prerelease

Unfortunately, I can't make it go though auto update right now, but you can download it and update manually.

[zachlatta]

:thumbsup: