begin work on a new feature selection unit test

Using a bag-of-words constructed from real data from a web newsfeed.
Enable the new test.
new test switched over to single-threaded
tests should clean up after themselves.

They keep leaving grunge in the  /tmp directory.  Annoying.
remove junk files left behind by test.
Merge pull request #173 from linas/moses

Moses dynamic feat-selection UTest