Fixed hash creation for Jobs

The creation of hashes for Jobs depended on serialize which in turn makes use of type information of the values to serialize. By passing a number from script and parsing string values (with possibly auto conversion), the hash for the same Job could be different. Therefore, a forced string conversion is introduced to normalize the values before the hash creation.

This should fix issue #4. 
I thought about restoring the original line when a job was not changed (some code is still somewhere in my stash) since the formatting of every job is changed on a rewrite. Therefore I didn't want to pass the preprocessed line.