New Versioning Scheme

[shibumi]

Currently, our README.md defines the following versioning scheme:

The versions will follow the spec. So if the spec is released at 1.0. 
Then all versions in the 1.x.y will follow the 1.x spec.

In #57 we realized how impractical this is, hence I thought about releasing a v1.0.0 and creating a v1.1.0 release after merging the aforementioned PR.

Also, I thought about dropping this version scheme in general and instead we could go with version directories: v1/ or v2/, like some other APIs do.

WDYT? @pombredanne @sschuberth

[shibumi]

Oh never mind.. while writing this, I realized the README.md actually mentions v1.x.y already 🤔 not sure what I thought.

How far away are we from spec -> v1.0?