Add 'android-sdk' cookbook

As discussed with @joshk, this cookbook has been intentionally *kept simple* and focused on the installation of Android SDK only. Additional cookbook (or refactoring) may come later, if we further need to install more parts of the Android Developer Tools (like emulators, ...)

### Open Issues:

 * The PR is based on master branch as requested by @joshk. It may not fully work with Chef 11 until some changes from 'bluebox' branch are merged back to master.
 * I want to make the cookbook interrupt itself if target node is not a Linux/i386 (see TODO marker)
 * While working on this cookbook, I noticed some small bugs in `/etc/profile` usage across travis-cookbooks, that lead user `travis` to source twice the statements defined in `/etc/profile.d/...`. This problem is **not** related to changes proposed here. See #154.

### ATTENTION:

This cookbook is for now designed for Linux/i386 arch only, because of Google Android SDK requirements. More details can be found in https://github.com/travis-ci/travis-worker/issues/56