Merge pull request #12 from melexis/master

Allow bundles in 'Installed' mode before starting to upgrade
Fix documentation for gt lt
Merge remote-tracking branch 'origin/master'

* origin/master:
  Allow bundles in 'Installed' mode before starting to upgrade
Change version to 1.6.3
Refactor switching the runlevel.

- Get the current runlevel before lowering the runlevel.
- Raise the runlevel to the original level in case of an exception.
- Raise the runlevel to the original level after performing the upgrade.
- Add documentation.
Change the version number
Merge pull request #13 from bhoflack/RESET_RUNLEVEL_AFTER_EXCEPTION

Reset runlevel after exception
ensure the start level is always increased again