Used string replace instead of regex (removed the import). Now detects when command is empty, and raises ValueError. Attempts to not recreate jobs that already exist. Saves lines in old crontab, and gets list of old jobs. Checks if in old crontab then compares interval and command equality.
Fixed style errors.
Finished unit tests for all current API functions.
Merge pull request #49 from BigFav/fnc4

Don't recreate jobs that haven't been modified
Merge branch 'rough'

Conflicts:
	megacron/edit.py