Partial Fix for Issue #29.   Biologically & formally equivalent tree representations were being rejected by the test code.  After the fix trees with swapped sister nodes are treated as OK, since the choice is arbitrary anyway.
Fixes Issue #29:  tip is replaced with tip.Name in a list comprehension prior to passing to getSubTree, which resolves test failures
Removes print statements from test_make_test_datasets.  Note that an assertion is still needed for test_make_distance_based_tree_randomizer, but this will be resolved as a seperate issue
Removing unneeded stdout, and switching the verbose default for minor functions (where output is usually only useful in debugging) to False.
Merge pull request #31 from zaneveld/exclude_tip_fix

Fixes Issue #29 Failures in test_make_test_datasets.py