Refactored dbm tests.

Doing a general refactoring to do continued development on dbm.  Separated the tests out to reflect the different layers, and removed some duplicate code.
Added unittest library as testing framework.
Added staticmethods to each class of tests to reflect the layer-specific checks.
Moved tests to nosetest.
Removed all reference to unittest.  Tests all pass using nosetest models/tests/test_dbm.py
Refactoring of only Binary layer unit tests for DBM.
Scaled back refactoring for this PR for test_dbm.py, limiting it to BinaryVector visible layer.  Other refactorings will follow pending a successful pull, followed by Ian's new tests.
Deleting erroneous second pass on even units in UpDown inference procedure.
A copy-paste bug was removed from UpDown (reference Ian), which did a second pass on even hidden units on each iteration.
Changed name of TestBinary class to TestBinaryVector.
Fixed typo for TestLinearVector and actually tested this time.
Merge pull request #1146 from rdevon/rbm

Rbm