* trying to fix plurals

remove bigram example as all examples now do bigrams

add test for tokenization, let ``words_`` be a dict

add colormaps, always try horizontal/vertical if other doesn't fit!

remove relative_scaling form simple.py

add matplotlib to dependencies

* fix setting of self.words_, special case for a single word

* add matplotlib to travis script

* set matplotlib backend in tests

* hack for old matplotlib