Add Python 3.5 to CI builds

[mark-adams]

Just noticed we don't have Python 3.5 set up for our CI builds. This adds Python 3.5 and changes some of our single version builds to use 3.5 instead of 3.4.

[coveralls]

Coverage remained the same at 100.0% when pulling fa302e2 on add-python-35 into d363ae9 on master.

[coveralls]

Coverage remained the same at 100.0% when pulling 3e034e1 on add-python-35 into d363ae9 on master.

[coveralls]

Coverage remained the same at 100.0% when pulling d02eaad on add-python-35 into c1290f0 on master.

[jpadilla]

@mark-adams awesome, thanks!