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
Much nicer looking HipChat notification message
Add Flowdock configuration option
Merge branch 'master' of github:errbit/errbit
Shrink "Notification Service" header down to "Notify", to reduce wasted space on apps index view.
check for MONGODB_URL if USE_ENV or HEROKU is set
Update README.md

Fixed Markdown syntax on "Jira Issue Integration"
Merge pull request #545 from williamn/patch-1

Update README.md [ci skip]
Merge pull request #542 from Stackato-Apps/master

check for MONGODB_URL if USE_ENV or HEROKU is set
Merge pull request #530 from nfedyashev/flowdock_improvement

Add Flowdock configuration option
Merge pull request #531 from brendonrapp/master

Nicer, friendlier HipChat notification message
Extract i18n key in apps/index view

Extract i18n key to allow translation in future.
Back to 'Notification Service' instead of 'Notify' introduce on
[f18a9814c2a04753f3c7946e2dce688cb81255ce]

see #531
Merge pull request #254 from concordia-publishing-house/simplify-err

Suggestion: Err should validate 'problem_id' and 'fingerprint'
Add some information in readme

* Information about the stack and buildpack on heroku create command
* Information about the compiling of asset when you upgrade

see #543
Merge branch 'master' of github.com:errbit/errbit
Fix errs creation

Issue introduce with PR #254 and break spec
Made the jira client switch ssl off if no https url is used
Merge pull request #550 from xenji/bugfix-529

Made the jira client switch ssl off if no https url is used