Merge tag '2.0.0alpha2' into develop

Version 2.0.0alpha2
added morfessor-train and morfessor-segment
Merge remote branch 'origin/develop' into develop
fixed lexicon's get_codelength - works now also for an empty model
Fix the Argument error for Python 3 when running morfessor without arguments
Remove progressbar as a requirement
Merge branch 'develop' of https://trac.ics.hut.fi/git/morfessor into develop
Bumped version to 2.0.0alpha3
Merge branch 'release-2.0.0alpha3'