Detailed comparisons to stdeb, dh-virtualenv and fpm

See also issue paylogic#1 on GitHub, requesting a comparison to fpm:
  paylogic#1

Finally got tests running properly on Travis CI, time for badges :-)

This closes issue paylogic#3 on GitHub:
  paylogic#3

Improve PackageToConvert.determine_package_architecture()

In 43961c2 I added the armv6l -> armhf
mapping to PackageConverter and I just noticed that PackageToConvert
didn't respect this change.

I'm not sure why PackageConverter and PackageToConvert both ended up
having separate ways to detect the current Debian architecture (I guess
this was left over from a previous refactoring) but clearly this logic
should be contained in a single place, not spread over multiple places
like it was before this change.

Bump deb-pkg-tools requirement to improve Python 3.x compatibility

Give up on conversion of package descriptions*

 1) It was always just a nice to have.
 2) I'm never going to get it working reliably.
 3) Right now it adds several "dead weight" dependencies.
 4) The "dead code" was reducing test coverage.

Log when control field overrides file is NOT found

Bug fix: Change initialization order

Re-enable auto-install runtime/configuration option

Upgrade to the new pip-accel

Workaround for dependency specifications like `pytz > dev'