Let android and iOS tests run on travis

[hypery2k]

• enable running test for Android on Travis

[hypery2k]

the build itself is now working for Android and iOS, but it takes very long and run into timing issue, so please @hdeshev maybe have a look?

[sis0k0]

Hi @hypery2k, thanks for the PR
We noticed that TravisCI builds usually take too much time (especially when mobile emulators are involved) and have a tendency to time out. That's why we decided to rely on internal testing infrastructure, which uses faster emulators and real devices instead.