Require mozrunner 6.5

https://bugzilla.mozilla.org/show_bug.cgi?id=1105837
Add support for win64 inbound

https://bugzilla.mozilla.org/show_bug.cgi?id=1105856
Merge pull request #138 from vaibhavmagarwal/mozregression-inbound64

Add support for win64 inbound
Bump version to 0.28

(skipped version 0.27, which I forgot to commit)
make FennecNightly call the base Nightly.__init__
refactor runinbound.py to remove copy/paste code and call base __init__ methods
move the _get_build_regex function to utils
rename get_date to parse_date and move parse_bits to the utils module