Make sure everyone is comparing Alphabets with equals(Object), not ==

…Since deserialization no longer returns the same object. But note that this is regardless a slight behavior change, since there are other ways in which Alphabet users could have constructed equivalent Alphabets, and the code previously did not detect this situation properly.

This change was proposed by Juan Cejuela.
Merge branch 'eh-fix-leaks'

Conflicts:
	src/cc/mallet/grmm/test/TestGenericAcrfData2TokenSequence.java
	src/cc/mallet/pipe/tests/TestPipeUtils.java
	src/cc/mallet/types/tests/TestLabelAlphabet.java