Merge pull request #25 from kenvandine/master

build fixes for Qt5 and Box2D 2.3
If the ImageLayer height isn't the same as the pixmap height,
scale the pixmap height to match.  The source image should
attempt to accomidate for the desired height to ensure the
quality of the scaled pixmap, but when the exact height isn't
known we should scale instead of crashing.
Merge pull request #26 from kenvandine/imagelayer_scale_height

Scale pixmap height if needed
Dropped support for Qt4, Qt5 is widely available now.
Fixed paratrooper demo's loading images from the resource
Merge pull request #27 from kenvandine/qt5_only

Dropped Qt4 support
Don't compare QQmlScriptString before setting it.  There seems to be
a bug in Qt when getting the scriptString from QML that breaks
comparison.  Setting it does actually work though.  This fixes
issue #22.
Merge pull request #28 from kenvandine/scriptbehavior_fix

ScriptBehavior fix
Merge branch 'master' into packaging