Updated .travis.yml
Implemented clone based on Anssi's suggestion.

Doesn't seem to be needed now, but better be safe than sorry.
Docs: Add example about using custom Tag
Merge pull request #149 from unho/docs_improvements

Docs: Add example about using custom Tag
Added support for prefetch_related on tags fields
added IDE to ignore
Made test python 2.6 compliant and removed gitignore item
more py 2.6 compliance
python 3.2 compatability
prefetch optimisation
related name for tag managers