Add 'instancetype' to pre-defined type names
Bump version to 0.8.0 (API change)
Fix __unsafe_unretained

The storage specified was misspelled as ’unsafe_retained’.
Three new ObjC quasiquoters

* ’objcprop’ for individual ObjC properties
* ’objcifdecls’ for ObjC @interface declarations
* ’objcimdecls’ for ObjC @implementation declarations
Add ObjC anti quotations $ifacedecl & $ifacedecls
Rename new anti quotes to $ifdecl and $ifdecls

* This is to be consistent with the naming of the quotations
More antiquotes in objc implementations
Document new ObjC quotes and antiquotes
Merge pull request #38 from mchakravarty/objcprop

ObjC: property, interface, and implementation quasiquotes & interface antiquotes