removed needless 'dispose' call

When the next context is requested, the old one is disposed automatically, anyway. And in previous stage3D versions, it's not possible to call "dispose" on the context without having it recreated at once. So it's better not to call it at all.
fixed error in parallel asset loading that could pop up with extended AssetManager class

see: http://forum.starling-framework.org/topic/asset-parsing-issue
avoiding any allocations in 'execute' for reasonably long argument lists
Added GradleFX build script
Added TravisCI build script
Improved build script with comments and cleanup
Refactored ANT script (modular targets, use standard SDK env. variables if present)
Improved ANT build script compatibility with Adobe AIR sdk
Improved maven build script (fixed sdk version to available one, added comments)
Updating maven script to flexmojos 7.0 with apache flex
Fixed Maven packaging
Fixed Maven temporary repo. checksum policy
Merge pull request #591 from vpmedia/feature-build-gradle

Added GradleFX build script
Merge pull request #593 from vpmedia/feature-ant-refactor

Refactoring of Ant build script
Merge pull request #592 from vpmedia/feature-travis-ci

Added TravisCI build script
Changed Mavenized FLEX SDK location to dedicated host
Merge pull request #594 from vpmedia/feature-maven-refactor

Refactoring of Maven build script
updated copyright headers in all source files
Added Travis build status to Readme
Merged gitignore files