Sentiment analysis on exhibition items.

New requirement: Pattern2.5, for analyzing tweets and data.
Warning: available on /api/m/<pk>/o/
Unittest: simple test, should stress more the server, to test pattern's cache
and twitter search.
Hide inappropriate language.
Sentiment feature over /o/<pk>

Item details now return new data: 'city' and 'sentiment'.
Merge branch 'master' into feature/sentiment

Conflicts:
	muse/rest/views.py
	requirements.txt
initial color for sentiment
Merge branch 'feature/sentiment'
Merge branch 'master' of github.com:youpony/aMuse