Ensure /usr/local/android-sdk/tools/bin is on $PATH
Ensure /usr/local/android-sdk/tools/bin is on $PATH

Recent versions of Android tools have essential tools in this
directory, while on older versions used "tools".
In particular, `sdkmanager` is found in "tools/bin".

craigcitro/travis-build,andyli/travis-build,craigcitro/travis-build,andyli/travis-build