added DTM wrapper, supports training on a corpus
removed some debug code
Added  Copyright  and some style/bug fixes
changed default params
minor doc&format fixes in DTM model
dtm wrapper: pep8 fixes
Merge pull request #1 from piskvorky/dtm-interface

minor doc&format fixes in DTM model
Merge branch 'dtm-interface' of https://github.com/Arttii/gensim into Arttii-dtm-interface

Conflicts:
	gensim/models/__init__.py
add & clean up docs for DTM
Merge branch 'Arttii-dtm-interface' into develop