args parsing
enhance robustness and messaging for command-line usage
improve --srilm-bin SRILM handling
implement merging
remove kenlm stuff. That can be accomplished outside this script.
moved unit tests to separate file:

because the mock module couldn't be found.
make merge_lms.py executable
add merge-lms step to pipeline.pl
Merge pull request #88 from lukeorland/feature.merge_lms

New script and pipeline script to merge all the ARPA-formatted language models