Merge pull request #15 from bjorn/master

Reuse the loaded map table rather than copying things out
Create new Custom Layer, more Callbacks

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2014-01-16 : v0.3.3
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* Added: Create new Custom Layer
* Added: Callbacks for all layers
* Added: Remove Layer
* Changed: Simplified sti.new()
Changed example
Object Layers

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2014-01-17 : v0.4.0
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* Added: Draw Object Layers
fixed offset, polygons

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2014-01-17 : v0.4.1
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* Fixed: Tiles incorrectly offset
* Fixed: Drawing concave polygons
Organized code

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2014-01-17 : v0.4.2
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* Changed: Organized library a little better
Layer draw offsets

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2014-01-18 : v0.4.3
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* Added: Layer draw offsets
Added link to documentation
derp?
formatting
Draw Range

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2014-01-19 : v0.5.0
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* Added: Draw Range optimization
Draw Range
Sprite Batches

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2014-01-19 : v0.6.0
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* Added: Sprite Batches
Fixed collision maps

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2014-01-19 : v0.6.1
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* Fixed: A bug causing the Collision Map to be nil
Fixed a scaling bug

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2014-01-20 : v0.6.2
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* Fixed: A scaling bug
Tile Flags

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2014-01-20 : v0.6.3
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* Added: Tile Flags (flip/rotation)
typo
Isometric Maps

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2014-01-24 : v0.6.4
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* Added: Isometric Maps
Staggered Maps

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2014-01-24 : v0.6.5
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* Added: Staggered Maps
Fixed spacing

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2014-01-24 : v0.6.6
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* Fixed: Spacing wasn't calculated properly