make cosmological priors safe to read/write to plain text

I made a couple of small modifications to the way the cosmological priors are written to disk so that they can be safely reloaded in the majority of instances.

This should resolve #355 (closed).

added 12 commits

• 22933fb8...5484acf8 - 10 commits from branch master
• 60f738f4 - Merge branch 'master' into load-cosmological-priors
• c9fc57cf - make python 2 test work

Compare with previous version

I had to modify the tests a little to make them run in python2. For some reason, the order of the arguments is shuffled, this means that the repr isn't the same as the original, but it definitely contains all the same characters. Presumably, this is a difference in how dictionaries are indexed between versions.

approved this merge request

approved this merge request

mentioned in commit 570c9cce

merged