Updated .gitignore
Removed the use_corpus and associated bloat code

There used to be a use_corpus parameter which came into play when
creating the corpus, and an if/else statement based on it but there
was never a case where we wanted to take the False branch, so just
got rid of all that.
Changed isA_symbols to contain only '@'

Used to contain '~@' as well, but it isn't used very much and
effectively doubles the number of attempted jumps that we have to do.
Made a new class for doing just WordNet testing

* AssociativeMemoryTester used to be a giant class. However, a lot
of the code in there was specific to testing using WordNet as the
underlying graph, which we don't always want to do if we want to
run quick, more controlled tests.

* So we made a new class WordnetAssociativeMemoryTester which
inherits from AssociativeMemoryTester, and contains all the code
for using WordNet, while AssociativeMemoryTester becomes a class
that can be used to quickly test associative memories.
Improved the associator constructor calls

Made the calls to the constructors of AssociativeMemory and
NeuralAssociativeMemory more coherent so that parameters
occur in the same order in both functions. Changed the calls
in run_script.py accordingly.
Added more tests

* Added tests for the 3 calls for running entire test epochs,
runBootstrap_jump, runBootstrap_hierarchical, runBootstrap_sentence.
These currently do not test the output, they just call the functions,
more of a test that they can run at all. Currently does both neural
and non-neural, might want to take out the neural tests so it runs
faster, since its not actually supposed to test the cleanup itself,
just the the tests are structured properly.

* Made better hierarchical test in test_neural_cleanup.py. Now uses
the networkx python lib to create the graph, much less code.