[TASK] Change userFunc reference for 6.2 compatibility

This one needs testing on 4.5 with thorough cache purge before pass. Might affect 4.x versions' ability to call the method.
Merge pull request #64 from NamelessCoder/62compat

[TASK] Change userFunc reference for 6.2 compatibility
[TASK] Update Travis script to install dependencies on-the-fly
[TASK] Correct path when installing dependencies in Travis script
[TASK] Sanitise legacy configuration support
[TASK] Improve performance of page template set resolve logic

By reordering, it's ensured that methods which are quite high in resource consumption are absolutely only called upon when needed.
[TASK] Sanitise cache key declaration
[TASK] Undo changes from optimisation with bad effect
Merge pull request #65 from NamelessCoder/legacysupport

[TASK] Sanitise legacy configuration support