Initial Galaxy front-end for normalize-by-median

add --out to normalize-by-median; --version

bonus: cleanup of -1 invalid exit value

To-do

- [ ] more unit tests
- [ ] functional galaxy tests
- [ ] test dependency installation
- [x] tool tips
- [x] hashtable reading / writing
- [x] general Galaxy help text
- [x] update Changelog again
- [ ] parameter validators (maybe?)
- [ ] setup tool shed
- [ ] document installation (update for filter-abund)