Fixed misspelled "capitalize" and added flash message to view

Fixed misspelled "capitalize" when creating error message for adding duplicate Compute Chargeback Rate
Added flash message definition to Chargeback Edit view

https://bugzilla.redhat.com/show_bug.cgi?id=1073366
Merge pull request #1159 from GregP/chargeback_rate_capitalize_msg

Fixed misspelled method name (capitalize)