CocoaPods and build.sh updates

- Updated podspec to support both iOS & OSX
- `clean` now removes all non git-versioned files (except `core/`)
- added `browser` target
- added `deploy` target
- added `pod-deploy` target
As BASH version 3 is preinstalled on OS X, I see no problem in using BASH features (please avoid version 4 features). The top of `build.sh` actually says that the script isn't strictly POSIX compliant.