cont: Resque monitoring, Per-plugin frequencies, and additional Redis monitoring

Regarding to issues with ruby-1.8.7 I have found a few small problems:

* lib/bipbip/plugin/resque.rb:32: ruby doesn't like comma after last param
* gem resque requires multi_json in higher version; for me works fine with 1.7.7; so suggest to add this to .gemspec?
* lib/bipbip/plugin/redis.rb:39: round() dosen't accept any params and returns integer in ruby 1.8.7 (http://ruby-doc.org/core-1.8.7/Float.html#method-i-round)