Fix leak
SpecHelper -> CDRSpecHelper

- SpecHelper.h is retained for compatibility with a deprecation warning,
  as it is likely to be imported at the top of users' spec files.
Don't include Cedar-iOS as a header directory in the Podspec

- This effectively namespaces the Cedar headers, preventing:
`#import "CDRSpecHelper.h`
and instead requiring:
`#import "Cedar-iOS/CDRSpecHelper.h`
Prefix CDRSpec's global currentSpec
Prefix public symbols from CDRFunctions.h, deprecating the original names
Update templates to account for the namespacing changes