CLC-2905 Redoing Rails 3.2.16 upgrade, with piecemeal bundle updates

https://jira.media.berkeley.edu/jira/browse/clc-2905 was the original Rails 3.2.16 upgrade, but asset precompilation broke, which is https://jira.media.berkeley.edu/jira/browse/clc-2908

Basically the fix was to do a piecemeal bundle update on specific gems, rather than a global "bundle update". I discovered that rails_admin introduced a vague version for bootstrap_sass, which caused a buggy bootstrap_sass 2.3.2.2 to slip in, breaking asset compilation. Fix is to lock rails_admin at 0.4.9 and bootstrap_sass at 2.3.2.0.