Add .travis.yml (#1833)
Add .travis.yml (#1833)

Some notes:

* Needed to use Java 8 instead of Java 7 as travis doesn’t support Java 7 anymore.

* Used armebi-v7a emulator instead of x86 as travis doesn’t support x86 emulator.

* By default, when using sdkmanager to install components, the license file will be automatically accepted by travis. However there is an issue that the android-sdk license file when installing ndk-bundle doesn’t get accepted right away; it will be timeout in about 2 mins before accepting the license.

* The whole build + test process took about 25 mins.
couchbase/couchbase-lite-android,couchbase/couchbase-lite-android