Merge remote-tracking branch 'glenjamin/more-form-stuff'
Use copy of assoc-conj instead of ring-codec's to avoid dependency hell
Simplify form tests in core

Precursor to adding more form field writing support
Separated out the testcases a bit
Attempted to assert on behaviour over implementation
Transposed fill-in tests
Add (choose selector option) function for select boxes

Supports picking a single option in a select box
via option name or option value