Revert "Fix up build.gradle"

This reverts commit a1a09ba3b1c5b09e6983f284076ec6b801c2dd53.

Only using the IDE plugins on subprojects causes `./gradlew idea` to
fail to generate the "root" project (i.e. `mygame.ipr`).
Update to LibGDX 0.9.9 stable.
Update to Gradle 1.8 stable.
Customise template.

Customise template to suit the needs of the project. Also add readme,
license, contributors, etc.