Use the same version numbering for the documentation and OSP-core: removes the need for a compatibility matrix at the landing page.

[kysrpex]

Right now, the documentation has different version numbers than the software. This leads to the need to include a compatibility matrix on the landing page (related to issue #78).

I propose to just use the same numbering for OSP-core itself and the corresponding documentation (or dropping some of the minor version numbers for the documentation). Many projects are doing this: Django, Pandas, Matplotlib, etc.