#2039 Accept block for download_links
#2039 Ensure that download_links supports stabby proc syntax `-> {}` by using `instance_exec`
#2039 Remove unused restricted AdminUser leftover from manual testing.
Deep copy the filters hash.

Filter :if and :unless options were being deleted and thus only
used for the first request.

Deep copy of the filters hash allow safe deletion of filters' options
like :if and :unless, to pass a clean set of options down the line.
Merge pull request #2523 from PChambino/patch-1

Don't delete :if and :unless from filters
Prefix columns classes with `col-`
Use class based on column name for AttributesTable rows
Use `parameterize` to generate class from column name
Class default to .row and .col
move installation instructions out of the README

by removing duplication it's easier to keep it updated
reword part of the README
update README so the sentence fits on a single line
use shields instead of badgr for Gittip badge
Merge pull request #2040 from creativecommunion/2039-accept-block-for-download_links

#2039 Accept block for download_links
add tests to illustrate symbol leakage problems
update pagination spec
fix batch action symbol leakage
fix url_for symbol leakage

url_for normally symbolizes the keys passed to it. This is a problem
for Active Admin, since we don't want to limit extensibility by
whitelisting which query parameters are persisted on the index page. We
get around this problem by passing the query parameters back into new
URL creation, namespaced under the `:params` key. This way they're
persisted, but arbitrary symbols aren't created in memory.
Merge pull request #1926 from Daxter/security-refactor

Security Fixes
add a note in the README about Rails 4 support