Fix image loader on IE; add loader test

`obj.src = ""` triggers the error event on IE while it doesn't on webkit
so adding a check for the type of browser fixes the error.

See #549 for more details.
CommonJS approach
Delete php build script and crafty-local.js
Grunt watch task for continues building the crafty.js file.
Provide source-map support for a development version of Crafty.js
Update `getVersion` method

Using `require` is possible to dinamically get library version from
package.json `version` property.
Merge pull request #568 from kevinsimper/commonjs

Browserify Crafty.js
Merge pull request #571 from potomak/feature/fix-version-method

Feature/fix version method
Merge branch 'feature/fix-IE-assets-loading-error' of git://github.com/potomak/Crafty into potomak-feature/fix-IE-assets-loading-error

Conflicts:
	Gruntfile.js
Text property family should have singlequotes around the string
Merge pull request #574 from kevinsimper/textFontFamily

Text property family should have singlequotes around the string
delete references to crafty-local.js in tests
Remove old PHP API documentation build system

See bc7ce76
Remove browserify dependency

It's not used anywhere besides in grunt-browserify, which already defines it as
a peer dependency. It will still be installed to `node_modules` upon
`npm install` anyways.
Merge pull request #582 from KenanY/develop

Remove browserify dependency
Merge pull request #579 from sbyrnes321/develop

delete references to crafty-local.js in tests
Typo correction: 'poly' to 'circle'.
Merge pull request #584 from likethemammal/typoCircle

Typo correction in Crafty.circle documentation: 'poly' to 'circle'
Remove vestigal component 'Physics'
Merge pull request #585 from starwed/remove-physics

Remove vestigal component 'Physics'