Update setup.py to allow for running it with `develop` argument
Add requirements.txt for development
Update version and versioning scheme
Remove gzip without extension test

gzip should not be treated as a format of its own as it applies to
all genomic tracks format. Thus, we can dispense with the test
case for gzip files without an extension.
Add missing gzip test file
Update gMiner.manipulate to track.manips
Add proper exception for handling missing executables
Update bigwig test to only run when executable is present
Add .travis.yml file