Renaming "lib" directory to "engine".
Attempting to pre-load assets of player and enemies before they're rendered.
Adding comment to detectAreaExit and renaming variables.
Merge branch 'modularisation' into gh-pages

* modularisation:
  Adding comment to detectAreaExit and renaming variables.
  Attempting to pre-load assets of player and enemies before they're rendered.
  Renaming "lib" directory to "engine".