report the actual url as request_url

Reporting the hash turns (for me) out to be error prone as I do not get the actual host.
move the validations for error_class and environment from Err to Problem

Problems are the models rendered in the UI now, not Errs. Errs are functioning as a glorified hash table. It makes more sense to validate problems.

Also, this paves the way for the next commit, so that no functionality is lost in the subsequent refactor.
Errs are like a hash table whose values are arrays of notices and whose keys are a composite of error_class + component + action + environment + backtrace[0..3].

These fields no longer need to be cached separately on Err because they are now cached on Problem.

This commit combines all those values into one simple key: fingerprint. This should:

 - Make err lookups faster
 - Make it easier to reason about, test, and replace the fingerprint algorithm
 - Make the relationship between Problems, Errs, and Notices clearer
[WIP] Start refactoring the problems_controller.

1) Limit some before_filter using the expose system
2) Extract some view test in view spec instead of controller spec
[WIP] refactor the problems_controller

Extract the filter `find_problem` in decent_exposure to get this problem
Treat message as CDATA to avoid invalid XML
Added jira as new issue tracker
Properly escape backtrace attributes to avoid invalid XML
add newrelic
Merge pull request #514 from mildavw/master

fix for notifier.js sending invalid XML
Merge pull request #517 from roryf/master

Fixes notifier.js sending invalid XML in backtrace lines
update changelog with new Pull request merge [ci-skip]
Pass problem when you UpdateProblemCache by rake task

Fix #518
update changelog with issue fix [ci-skip]
Sign in input set type=email for mobile browsers keyboard
Email only unless user_has_username
Merge pull request #519 from nyaa/email_input

Sign in: email input type=email for mobile browsers keyboard
Add documentation about all Env variable usage

Errbit can be config anly by ENV variable. We need a complete
documentation about it and improve this variable capabilities with not
only Heroku point of view
Improve information about ENV configuration
Fix spec because now the spec use TimeZone too in Mongoid