Cosmetic changes to FastaConverter and FastaConverterSuite.

Just making a few little cosmetic changes to FastaConverter, to make part of the code more readable.

Also, added a second condition to one of the tests in FastaConverterSuite, to check that the reassembled
sequence (which had been created, but wasn't being used) matched what was in the original file.
Added a note about rebasing-off-master to CONTRIBUTING.md

Contributors should rebase their feature branches off of master (and
moderators should double-check that this is the case) before the feature
branch can (will be) merged.
Merge pull request #249 from genomebridge/cosmetic-changes

Cosmetic changes to FastaConverter and FastaConverterSuite.
Merge pull request #252 from genomebridge/rererebase

Added a note about rebasing-off-master to CONTRIBUTING.md
Adding ADAM to SAM conversion.