Corpora slicing

- Corpora now implement slicing syntax. For example, corpus[::2] gives
  you even documents
- Re-serialize corpora to generate matching .index files
- Make IndexedCorpus return a SlicedCorpus (generator)
Merge pull request #246 from piskvorky/corpora_slicing

Corpora slicing
Distributed LDA/LSI Python3 compatibility

Fixed import of the queue/Queue module to be compatible with
both Python2 and Python3
Merge pull request #249 from bonzanini/distributed-py3

Distributed LDA/LSI Python3 compatibility
update version of dependencies
Merge branch 'develop' of github.com:piskvorky/gensim into develop
Merge pull request #1 from piskvorky/develop

Grabbing latest updates.