Factor out maximum k-size as KSIZE_MAX and throw a python exception if the user supplies a larger one to the hash functions
add code of conduct
clarify notification process
wording tweaks courtesy @ctb & @camillescott
Merge pull request #664 from ged-lab/feature/code-of-conduct

add code of conduct
Merge branch 'master' of https://github.com/ged-lab/khmer into fix/658
Update ChangeLog for fix for Issue 658
Merge pull request #663 from pgarland/fix/658

Fix Issue 658, max ksize silliness in the C++ code
Merge branch 'master' of github.com:ged-lab/khmer into update/streaming