Make sure that Checker does indeed ignore the names given in the "pyflakes_ignore" setting.

PyFlakes' Checker wasn't honoring the "pyflakes_ignore" setting. Instead of modifying a global, use Checker's "builtins" parameter when calling its constructor.
fixed bug that make impossible to use the linter if gutter_marks are disabled. Fixes #23
- added to readme
- added shortcut to settings files to main menu
- fixed issue #23
Merge pull request #22 from OscarL/patch-1

Make sure that Checker does indeed ignore the names given in the "pyflakes_ignore" setting.
small refactor in server.py to follow PEP-8
total refactor of sublime_python_linting.py file:

    * Fixed several PEP8 violations
    * Made the code more DRY
    * Added some decorator
    * Some big methods has been splitted in serveral methods
    * Changes are been tested and them are working fine
some PEP-8 violation fixed on server/linter.py
merged