set up travis/appveyor CI

[conundrumer]

also update readme (update the CI urls and uncomment the CI status) when that happens

[piedoom]

#2 merged and 4bfe2df updated badges.

As of now, only I have access to Travis and Appveyor, so I recommend at some point we create accounts on those services so we can have a group of people able to be administrator for the CI.