Wheels with capitalized names can cause name comparison to fail

[ScottyMJacobson]

Came across this when trying to install the "Markdown" package by putting "markdown" in requirements.txt

Traceback (most recent call last): File "/Users/scottyjacobson/Documents/Dev/accountable/env/bin/peep", line 11, in <module> sys.exit(main()) File "/Users/scottyjacobson/Documents/Dev/accountable/env/lib/python2.7/site-packages/peep.py", line 874, in main return commands[argv[1]](argv[2:]) File "/Users/scottyjacobson/Documents/Dev/accountable/env/lib/python2.7/site-packages/peep.py", line 846, in peep_install first_every_last(buckets[c], *printers) File "/Users/scottyjacobson/Documents/Dev/accountable/env/lib/python2.7/site-packages/peep.py", line 782, in first_every_last every(item) File "/Users/scottyjacobson/Documents/Dev/accountable/env/lib/python2.7/site-packages/peep.py", line 843, in <lambda> lambda r: out(r.error() + '\n'), File "/Users/scottyjacobson/Documents/Dev/accountable/env/lib/python2.7/site-packages/peep.py", line 712, in error line = '%s==%s' % (self._name(), self._version()) File "/Users/scottyjacobson/Documents/Dev/accountable/env/lib/python2.7/site-packages/peep.py", line 417, in _version return get_version(self._downloaded_filename(), self._project_name()) File "/Users/scottyjacobson/Documents/Dev/accountable/env/lib/python2.7/site-packages/peep.py", line 405, in version_of_wheel give_up(filename, whl_package_name) File "/Users/scottyjacobson/Documents/Dev/accountable/env/lib/python2.7/site-packages/peep.py", line 412, in give_up (filename, package_name)) RuntimeError: The archive 'Markdown-2.6.2-py2.py3-none-any.whl' didn't start with the package name 'Markdown', so I couldn't figure out the version number. My bad; improve me.

Not sure if this is expected behavior (should peep be case-sensitive?), or it just needs an improved error message, but the easy fix would be check the .lower() of each before failing (suggested in #104)