Moves sanic/sanic.py to sanic/app.py

Functionality wise this won't change much for most users, unless you
were directly importing from `sanic.sanic` in which case I am sorry if
you're affected by this.

Main motivation was because jedi autocompletion didn't work with this
and we were using relative imports to compensate for the fact that
having a module inside of your module with the same name creates major
namespace problems.

sanic/__init__.py

@@ -1,4 +1,4 @@
-from .sanic import Sanic
+from .app import Sanic
 from .blueprints import Blueprint
 
 __version__ = '0.3.1'