Fix Qt version number requirement
Merge pull request #173 from gladhorn/version

Fix Qt version number requirement
Fix qch doc build

This will allow the docs to show up in
Qt Creator and Assistant.
Merge pull request #174 from gladhorn/docs

Fix qch doc build
Merge pull request #175 from nierob/master

Small improvements
Fixup docs a bit
Merge pull request #176 from gladhorn/master

docs
Remove unused variable.
Fix typos in documentation.