Github: Bugfix: Wrong comparison of repository name

On Github the repository names musn't be lowercase and without blanks.

Because of that the comparison is wrong.
The repository name send in the payload-data by Github could be something like
``` RePoSiToy_NamE ```
But the data for ``` hub_reponame ``` has to be entered lowercase in the settings:
https://github.com/mantisbt-plugins/source-integration/blob/master/SourceGithub/lang/strings_english.txt#L12

So if the two values differ no import is possible.