viewport for IE9/10, let it can init again.

  I need to use Crafty.stop(), and then use init to restart it, actually the point is to init() again. It seems strange, but I encounter a situation that the Crafty appears in one div, then it must appear in another div. When it is in IE10, I can't init for a second time just because configurable default to be false.
Merge pull request #608 from txcodelife/develop

viewport for IE9/10, let it can init again.
Add `avoidCss3dTransforms` flag

CSS 3D Transforms are used to set DOM entities position, this should
increase performances as these operations are hardware-accelerated but
using them for positioning makes CSS effects unavailable.

By setting this flag to true you can force DOM entities positioning
using left and top CSS properties.
Merge pull request #609 from potomak/feature/optional-css-3d-transform

Add `avoidCss3dTransform` flag