Merge pull request #27 from mobli/master

Fix files missing in new projects
Added constants to interfaces

Added constants to interfaces. For the moment, constants can only be
used by using the full qualified name. For instance:

let myvar = MyProject\MyInterface:: MY_CONST;

Added forced regeneration of intermediate representation if
zephir-parser is updated (based on mtime).
Added better check to reconfigure the extension if files are
added/deleted.