Bump version to something readable + semver

[jpic]

Counting the 9s is a bit tiring, particularely when debugging version conflicts. I suppose this is because html5lib is not judged mature enough to be released as 1.0. This patch proposes moving from 0.999999 to 0.1.0 and at the same time proposes to adopt the semver standard.

[gsnedders]

0.1.0 < 0.9999999999, so that doesn't work, so I'm just closing this; discussion should probably happen in #282. The only way out of this wormhole at this point is 0.10000000000 or similar (I didn't count the zeros!) and then ignore all but the trailing zero (i.e., 0.10000000001 as the following release); as mentioned in the other issue, the right approach is almost certainly to just actually document what the public API is and release a 1.0 soon thereafter.