Added support for terms command

[oscargus]

Replaces #6 by introducing \terms{cells}{content}.

\minterms, \maxterms, and \indeterminants now use \terms underneath.

An example is also added to the manual, but due to a line break, it does not look so good.

No explicit tests (although I got slightly longer in the test now, diff-pdf was missing and I'm currently not in the situation to be able install it properly).

[2pi]

Thank you very much!

I've fixed some indentations, added some test cases and fixed the documentation issues.

Before I merge I would just like to make sure that your contributions (and possible future contributions) to karnaugh-map are under CC BY-SA as the rest of the codebase? Oh wait, it's a ShareAlike license, hence (according to my interpretation) you must release it under the same license if you release any modifications to karnaugh-map!? Right? I probably should have emphasized this earlier! Sorry!

Anyway would adding

Contributors include Oscar Gustafsson.

to the end of https://github.com/2pi/karnaugh-map/blob/master/README.md#license suffice as attribution? And therefore changing the top part of the karnaugh-map.dtx file similarly. Finally changing the copyright line to

Copyright (C) 2015 Mattias Jacobsson and contributors

[oscargus]

I am open to any solution regarding license and acknowledgement. While not fully understanding (going into details) the license issue, trusting you fully there, I think your acknowledgement suggestion sounds just fine.

Maybe updating the copyright year?

[2pi]

Great, thanks! To be honest I've a hard time understanding it myself, this is the main reason the initial release was delayed about a year. However to my understanding this is how it supposed to work.

I'll fix the year too.

[2pi]

Thanks for your contribution 👍