cleanup: drop an empty section header

compat: drop some <hg-3.4 compatibility code The `hg commit` commands has a -i flag for ages now.

README: more update to prepare for pypi upload * mention the evolve.serveronly extension, * remove help related to topic into a different README file.

evolve: update the capabilities and commands name for obshashrange We makes is clear that these version are useful for earlier testing but they are not ready for any kind of real usage yet.

README: more change to have a pretty rendering on pypi We moves section around and fixes some markup.

MANIFEST.in: fix various mismatch check-manifest is no longer complaining

README: rework install instruction For both evolve and topic. The topic introduction is updated too.

README: rework the intro Less scary wording (similar to the wiki changes) and point to the user mailing list.

rangeobshash: minor cleanup of the obshash code We achieved minor speedup by delaying the hashing until we know it is needed.

stablerange: remove call to 'repo.revs' It turned out that the percentage of time spend parsing the revset string was two digits, so we compute de heads inline.

stablerange: reuse node calculation as much as possible We have a property cache with that value, so we just reuse it.

stablerange: adds some caching of the subranges The goal of subranges is to be as reusable as possible, so we cache the subrange relationship to take advantage of this.

stablerange: operate on an unfiltered repository We only do operation on ancestors so using unfiltered is fine.

depth: use lower lever function to compute missing The time spend parsing the revset is noticeable.

depth: update depth to code to reuse ancestors depth Computing the depth of all N revs is no longer 'O(N**2)'