Junit observer fix

[cogmission]

fixes #434

• Added TestObserver solution found by @fergalbyrne
• Inserted TestObserver in all relevant tests
• Created new test base class to handle new test remedy

@rhyolight please approve

[coveralls]

Coverage increased (+0.04%) to 81.124% when pulling 9ef5252 on cogmission:junit_observer_fix into 227feb0 on numenta:master.

[rhyolight]

Wow, you've got tests for your tests!

[cogmission]

@rhyolight That's funny... :-)

But it really shows the vulnerability of putting assertions in Observers under certain circumstances, and clearly demonstrates the potential problem within HTM.Java's NAPI if it's not handled correctly. So it mostly acts as a way to document the "preferred" testing idiom.