General clean up of documentation

[drvinceknight]

I think a good detailed reread of the documentation is needed. I've noticed various small little inconsistencies and there could be more. I'm not suggesting a restructure, just fixing minor errors here and there. For example here: http://axelrod.readthedocs.io/en/latest/tutorials/getting_started/tournament_results.html

There is this line:

Note: Here using string representation to deal with floating point numbers:

Which is complete nonsense (I wrote that) and a relic of what I first wrote before simplifying how the doctests worked.

So I think this just needs someone to read through the docs and pick everything up.

Another example is that we have some places where we write:

import axelrod

and others:

import axelrod as axl

Not actually a problem but could be nice to keep the same for consistency.

Whoever does this: note that it's now possible to include ... as the output of doctests. This might be helpful.

[drvinceknight]

I'll pick this up.