Don't use PyPI mirrors when installing packages

The implementation of a content delivery network (CDN) for PyPI has
significantly improved PyPI's performance. It is now faster and more
reliable to use the CDB and PyPI's mirrors.
Update service badges for README

Adds a badge for latest version on PyPI and relocates it and the
TravisCI badge to introduction.
Update Python magic strings

Use the Python magic string definitions file from libmagic 5.14.
Discontinue use of distribute_setup.py

Most users will already have distribute or setuptools installed. Users
who don't likely have not installed them intentionally.
Update version to 1.6

Minor version incremented for new release.