allow setting of sourceFile.name and sourceFile.path
follow project conventions
Merge pull request #26 from isaksky/mutable-sourcefile-props

Mutable sourcefile props
Update README.md
Update podspec.
added support for generating uuid based keys for XCKeyBuilder
added 'duplicate' method for XCBuildConfiguration
pulled out some raw stuff from XCProject to control project more broadly from outwards
added support for duplicating XCTarget objects
added some notes about how to duplicate target to main readme
Merge pull request #27 from smirn0v/master

Support for duplicating xcode targets
Update README.md
local