Cleanup files:

The following has been removed:
- MYMETA.yml
- Makefile
- pm_to_blib
- blib/

They are all generated from the distribution builder and should not be
committed into the repo, since they are generated each time and mean
nothing in and of themselves

The following has been added:
- .gitignore: lists all the files that should be ignored so we can make
  sure none of those are accidentally added to the repo again.