More tkinter-related fixes:

1) use lower-cased tkinter module name (uppercased may fail in Python 3.x on case-sensitive filesystems, and lower-cased tkinter it is fixed by nltk.compat for Python 3.x);
2) imports in nltk.sem.drt_glue_demo are fixed (I didn't try the demo, but the code looks OK - I think it should work in 3.x as-is)
up-to-date urls for megam
Merge pull request #370 from kmike/megam-is-moved

up-to-date urls for megam
Demo functions for Baum Welch are fixed. See GH-69, GH-100.

They were broken in this commit: https://github.com/nltk/nltk/commit/9738e3e5027361255fc151b0dc7e1dd59ebeced2
PY3: fix nltk.classify.utils.names_demo (thanks Janosch Gräf for the report and a patch)
PY3: pickling of FreqDist is fixed (thanks @jgraef)
Merge pull request #369 from kmike/more-tkinter-fixes

Small tkinter-related fixes