Add config item for date format

[mbucc]

Add config item for date format

[kael-shipman]

I just decided to dig into this anyway and discovered that it may be more disruptive to your work than I had hoped :(. I found out that you're currently storing versions as integers in the db, and furthermore, you're padding them to 10 characters. While I think a switch to varchar/text from integer is innocent enough, I couldn't find a good function right off (in all databases) to guarantee successful lexical sorting in the event that the unix timestamp gets longer by a digit.

That said, that won't happen for quite some time...... Open to solutions either way.

[kael-shipman]

@mbucc any thoughts on this?

[mbucc]

This came up before (issue #32). I prefer epoch seconds because they represent a timezone.
Also, a human readable date format is in the first few lines of the generated file.

I suppose an option to list migrations that converted the timestamp on the file name to a human readable format would be useful.

[kael-shipman]

I'll close this in favor of #32, but I'm going to leave some comments there ;).