Allow predicates combinations to include functions
Merge pull request #98 from alphagov/combine_function_predicates

Allow predicates combinations to include functions
Don't humanize strings
Data partials pass back HTML which is getting humanized and breaking the casing in the HTML. This still allows Answer objects to be humanized but will stop data partials getting mangled. Slightly hacky fix, that should be refactored when looking at Answer objects more generally.
Refactor
Call .humanize on instances of Smartdown::Model::Answer::Base only