fix coverage command in makefile
make internal CRF methods private
cleanup some old function that survived during a failed rebase
COSMIT whitespace
Add basic linear chain CRF
Add Chain CRF and a very simple (buggy) example
trying to clean up chain_crf
initialize for ChainCRF
ENH user "directed" in ChainCRF, set default=True,  more / better docstrings.
TST add tests for chain crf.
ENH Add letters dataset
intermediate
add letter example
slight cleanup, fix folds in letters dataset, make example kind of work.
EXAMPLE fix up letters ocr example, make a nice plot