Trowl 0.5.1 -- Now with retweet action!

[Mageuzi]

Okay, this is a bit of a rough build. There are a few more changes I
want to make before making this final. (And, of course, do more
testing.) Once I'm happy with it, it will be 0.5.2. But if you'd
like to try out some of the basic retweet functionality that I have
already, feel free to check out this build:

http://mageuzi.com/trowl/trowl051-RT.zip

Some of the changes:
1. You can choose whether to have "official" retweets growled for each
account on the settings screen.
2. Retweeting a tweet in Trowl now uses the official retweet
mechanism. This means you cannot change the retweet text -- you only
have the option to send. I'm going to change the "New Tweet" screen
to make this more obvious before it's final.
3. The icon in the growl for a retweet is a combination of the
original tweet's avatar, the retweeter's avatar, and Twitter's retweet
icon. I tried to make it obvious that this is a retweet, but not too
confusing. Let me know if you like it, hate it, etc. :)