Added readme.md from old codeplex landing page

[enmaku]

[lakeman]

Note that this content is also currently on the github Wiki page. Personally I'd prefer to see a readme.

Also, can we add a cheat sheet for all supported operators & functions?

[ForestFeather]

I second @lakeman's request.

[yallie]

Also, can we add a cheat sheet for all supported operators & functions?

https://github.com/ncalc/ncalc/wiki/Operators https://github.com/ncalc/ncalc/wiki/Functions