Ignore concerns in app/models/concerns

Fixes #1636
Embed bootstrap-sass (locked at version 2.3.2.2).
Failing spec for #1714
Merge remote-tracking branch 'stympy/patch-1'
Added compability for Font-Awesome 4

Font awesome 4 introduced a new naming convention.
I did'nt use new naming convention because:
 * It's backward incompatible and people still use old version of Font-Awesome
 * rails_admin use old naming convention(icon-*) in javascripts.

I added a new scss file which add compability for Font-Awsome 4 uwing extend.
Point poltergeist to master. Refs #1804
Merge pull request #1809 from ideadapt/field-help-i18n

Support override of field help text via i18n.
emphasize that help requests go to the mailing list

We're still getting "how do I do this?" issues so here's an attempt to
make it even clearer that these go to the mailing list.
Merge pull request #1799 from jcoleman/vendorize-bootstrap-2

Embed bootstrap-sass (locked at version 2.3.2.2).
Merge pull request #1814 from bukhamseen/font-awesome-4

Added compability for Font-Awesome 4
Merge branch 'master' of https://github.com/sferik/rails_admin