postgis-{v}-scripts are included with postgis
remove `dpkg_autostart` cruft:

* `dpkg_autostart` isn't used any more, and this
  recipe doesn't start the service anyway, it just
  installs header files
* closes #48
make version check for 9.3 more robust
add contribution from @jherdman to the README
bump default postgresql to 9.3 and postgis to 2.1
note updated default versions
Merge pull request #50 from phlipper/version-bumps

Bump default versions