Fixes compilation issues on Swift 1.2

I had to add the 'context' and 'tag' parameters to DDLogXXX
functions to make it compile. It seems that this is a bug in
the Swift compiler with optional arguments and the use
of @autoclosure.

Podspec version set to 2.0.0

Bumped podspec version

Merge pull request CocoaLumberjack#417 from rivera-ernesto/rc

Last pull request for RC

Bump version

Bump beta version

Bump beta version

2.0.0-beta podspec

Bumped podspec version to 1.9.2

Bumped spec version to 1.9.1