Remove Xcode projects

* Xcode is no longer required to launch tests;
* Use rake for building and running tests;
* Rename main.c to tests.c;
* Use _NSGetArgv() for accessing the program name from within a test
case;
Add custom CCFLAGS field to each spec

So now we can test, for instance, different optimization levels
Add function for generating filename for a spec
Remove :result field from a spec's structure

This filed will be created in runtime
Fix a line that crushes everything
Merge branch 'remove-xcode-project' into develop

Remove Xcode project.

* Xcode is no longer required in order to launch tests;
* Use rake for building and running tests;
* Rename main.c to tests.c;
* Use _NSGetArgv() for accessing the program name from within a test
case;