Peg bootstrap_form to 2.0.1

bootstrap_form 2.1 changes some form input names and introduces a
problem with Blacklight configuration-backed forms. See
https://travis-ci.org/sul-dlss/spotlight/jobs/22049647#L537
Merge pull request #602 from sul-dlss/bs_form_201

Peg bootstrap_form to 2.0.1