Merge pull request #11 from neoneye/master

Xcode: Add ~/include to header search path.

.gitignore: Ignore Xcode 4 per-user files.
Add receive buffer method and fix bugs about checking return value of zmq_recvmsg and zmq_sendmsg
Fixed method name and parameter's type
Fix return value verification for receiveWithBuffer:length:flags
Merge pull request #12 from codingguy/master

Add receive buffer method and fix bugs about checking return value