Beggining refactoring and adding python3 support

The bukget module is now moved to pybukget.bukget. I will possibly move it to pybukit.low_level_api and make pybukget.bukget a high level api, which returns Plugin objects
Made new functions for all api functions in pybuket.api

Left is the classes(Plugin, Category and Author)
Should be pretty much done now
Fix for py2
remove debug messages
Some fixing

fix _ensure_slug in api, and raise exception if slug is not in plugin objects. override __hash__ of Plugin objects
Typo
refactored pybukget package to bukget
Fixing some bugs
Fixed a bug with plugin_download
Small fix
Merge pull request #1 from CubeEngineDev/refactor

Refactor, objects instead of built in types and py3 support