Ticket #12 : removed the previous hack-ish parallax layer code

Todo :
* implement the CSS -like repeat field (Ticket #124)
* update tutorial (Ticket #100) and documentation (html/github)
* clean-up any remaining messy code
* wait for the next Tiled release with official Image Layer Support
Ticket #124: added the "repeat" field for later reference (when working offline)
Added proper documentation for the `ratio` property
Stop using local copy of the library, and refer to parent directory for the last build
Ticket #100 : replaced obsolete "paralax" layers stuff by the new Image Layer

TODO :
* Update screenshots in the tutorial when an OSX version is available
(only windows nighty build are available for now)
Ticket #124 : fixed `repeat` variable scope
Ticket #100 : added missing ImageLayer Property screenshot (thanks @parasyte) and other documentation improvements
Ticket #100: update screenshot with something better matching the tutorial content (thanks Parasyte)
Ticket #100 : added back the missing Image Layer
Ticket #124 : add `repeat` property handling
Merge branch 'ImageLayer-cleaning' of https://github.com/obiot/melonJS into ImageLayer-cleaning
Merge remote-tracking branch 'origin/master' into ImageLayer-cleaning
Merge pull request #151 from nvlbg/master

Adds object pooling into me.entityPool
small cosmetic update (indent)
Ticket #151 : Fix Combo (see details)

- fix entity instantiation when not using object pooling
- make `me.game.remove()` call `me.entityPool.freeInstance()` and not
the opposite (object can me removed using the regular `me.game.remove()`
function
- stop complaining about unfound entities in
`me.entityPool.freeInstance()`, so that non "pooled" object can be
removed without errors
- fix an issue with object (re)initialization (missing properties
initialization in the `SpriteObject` constructor)
- misc typo and variable renaming
Added back a `collide` wrapper function in ObjectEntity
Added a `collideType` function to check for collision with a specific type
Removed the test on `isEntity` since the `collidable` property is actually only defined in Entity Object
Fixed the function call (with the right one)
Ticket #108 : added the possibility to pass arguments to the plugin constructor (through the register function)