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
Uses https-links for gravatar when using ssl
Cleanup problems_helper_spec
Makes avatar url tests in problem_helper_spec compatible with ruby 1.8
Merge pull request #534 from arthurnn/fix_gemfile_lock

update safe_yaml, as 0.9.4 was yanked
Merge branch 'master' of github:errbit/errbit
Shrink "Notification Service" header down to "Notify", to reduce wasted space on apps index view.
Sort list of apps to copy settings from.
use strong_parameters on decent_exposure

See https://github.com/voxdolo/decent_exposure/wiki/Strategies:-Use-with-strong_parameters
on how to use strong_parameters with decent_exposure
Merge pull request #535 from arthurnn/strong_param

use strong_parameters on decent_exposure
Merge pull request #532 from jeroenj/gravatar-ssl

Uses https-links for gravatar when using ssl
Update Devise gem to fix security issue
Add some information about contributors of Errbit project

[ci-skip]
Merge pull request #536 from 2called-chaos/fix_pull_464_sort_applist

Sort list of apps to copy settings from.
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]