Update Travis-CI configuration to use the new image they recommended us.

[pedrovgs]

As a bit more information, this new Android image comes with:

• Android SDK 25.2.3
• build-tools-25.0.2
• The new sdkmanager tool - a command line tool that allows you to view, install, update, and uninstall packages for the Android SDK. Replaces the previous android tool, see https://developer.android.com/studio/tools/help/android.html
• Also, the new Android image should be retro-compatible. See the full list of Android SDK components that can be specified in the .travis.yml file, including build-tools-26.0.0-preview.

[Serchinastico]

Any updates on this? Looks like the android-22 target doesn't exist

[pedrovgs]

@Serchinastico the issue is related to the backward compatibility the new Travis image provides. We can close this PR if you want. It's open right now just for helping Travis CI developers. @iriberri and I thought it could be a good idea.

[Serchinastico]

It's alright, we can keep it open, just wanted to add some context to the PR :)

[albodelu]

My thoughts on this topic in this SO response.

The answer Includes working samples like this one using your Dexter library prior to the VMs update.

I want to combine solutions in a more minimalist YAML file using Dexter and Rosie soon.

We need a working Travis-ci configuration to fix this Dexter issue.

[albodelu]

@Serchinastico read this line, android-22 component is missing.

Skipping 'ARM EABI v7a System Image, Android API 22, revision 2'; it depends on 'SDK Platform Android 5.1.1, API 22, revision 2' which was not installed.

We always need to install the latest platform and the platform used by the emulator.