Absolute_import modules and remove unused imports

This was done in order to prepare for py3k port. Python 3 uses only
absolute imports and Python 2.7 supports that as well.

I took an opportunity to remove unused imports in order to clean up the
headers. This will lower the barrier for pottential contributors by
removing the unnecessary confusion when there is a random `import gtk`
in the header.

I renamed the main `rapid.py` file in order to avoid any possible
clashes. However, since it is about 4k SLOC, it should be split in the
future either way.

Signed-off-by: Ignas Anikevicius (gns_ank) <anikevicius@gmail.com>