Run tests against multiple versions of Python about rst2rst

[mcepl]

Travis? And really, support for 2.5 in 2018? I feel super-conservative, when I support 2.6 in M2Crypto.

[benoitbryon]

Of course 2.5 looks deprecated now in 2018! This issue was created in 2013 :D
Feel free to adapt versions to current Python standards.

Note : I'm not active as a developer right now and have little time and motivation to follow the issues and maintain software... Tell me if you'd like to take the lead on rst2rst ;)

[mcepl]

Sorry, I have already too many zombies I drag from their graves. The best I can offer you is the pull request establishing testing on Travis CI. Would you be interested?

Or wouldn't it be better to push this code to the upstream docutils?

[benoitbryon]

Thank you for the proposal @mcepl. As I don't give time to this repository (and to coding) at the moment, I can't promise to review then maintain your contribution... So unless you (or someone else) take the lead, I can't promise it is useful to spend time on this repository at the moment :(

Feel free to propose this code to docutils: that's a good idea! Just notice that rst2rst isn't feature complete, so in my opinion (and coding skills) it is quite a challenge to complete rst2rst then push to docutils.