Implement documentation endpoint

[MeiSign]

From @schleichardt on January 28, 2015 13:37

controllers.Documentation#showDocumentation

Copied from original issue: HTW-Projekt-2014-Commercetools/api#5

[MeiSign]

From @peter-gerhard on January 28, 2015 18:10

added redirect to readme.md for now

[MeiSign]

Wiki files should not be in the same folder with our API Sources. We could consider putting them in the ressources package but I think the wiki should be a separate project...

[MeiSign]

From @sasfeld on January 30, 2015 9:28

The advantage: Write once and deliver only the API documentation. By including the doc as Git submodule, we still have the repos separated.
We could also deliver the complete README.MD - or fall back to a hardcoded and duplicated solution which I wanted to prevent.

Any opinions?