Adium 1.5.1

[Evan Schoenberg]

libpurple has been updated to 2.10.4 with 2 security fixes, and I'd also like to have us distributing a Developer ID signed binary. 

We may need to include some explicit parameters (the designated requirement) in the codesign line used in the release script, but I'm not positive with our current OS X targeting; we're ok on 10.7 without but 10.6.8 may need
it to behave properly.

Any objections to a beta in the next couple days?

-Evan