Update Capybara
Remove unsupported option
Fix comparison tests
Fix export group/reports CSV tests

Reason: https://github.com/jnicklas/capybara/issues/952
Fix import API test cases
Fix manage per feature results tests
Fix manage reports tests
Fix manage view passrate tests
Fix merge api tests
Fix NFT trend graph tests
Fix rename categories test
Commented out a test case
Fix RSS test and functionality

In addition to fixing RSS tests fixed the RSS link pointing to
wrong/nonexisting place when client side navigation is used. This issues
has existed for a looooong time unnoticed.
Fixed update api tests
Fixed edit report tests

Getting reports sorted by tested_at and created_at timestamps
occasionally returned an unexpected report. Added possibility to sort by
ID to make sure the just uploaded report is returned.
Random failures again, wait for ajax
Upgrade Nokogiri, XML-smart
Update rake
Upgrade Celluloid
Updated mysql and slim