remove travis build in favor of drone

.travis.yml

@@ -1,37 +0,0 @@
-sudo: false
-language: android
-android:
-  components:
-# first 'tools' updates SDK tools 'til last version ** in remote repository number 10 **
-  - tools
-# second 'tools' updates SDK tools 'til last version ** in remote repository number 11 ** (current last one)
-  - tools
-  - platform-tools
-  - build-tools-23.0.3
-  - android-23
-  - extra-android-m2repository
-  - sys-img-armeabi-v7a-android-23
-before_install:
-  - echo no | android create avd --force -n test -t $ANDROID_TARGET --abi $ANDROID_ABI -c 20M
-  - emulator -avd test -no-skin -no-audio -no-window &
-  - chmod +x ./wait_for_emulator.sh
-  - ./wait_for_emulator.sh
-script:
-# build app and assemble APK, in debug mode
-  - ./gradlew assembleDebug
-# run all the local unit tests of app module
-  - ./gradlew :testDebug
-# run all the instrumented tests of app module - DISABLED until we get an stable setup for Espresso in Travis
-# - ./gradlew connectedDebugAndroidTest --info
-# install app, then assemble and install instrumented tests of app module
-  - ./gradlew :installDebug
-  - ./gradlew :installDebugAndroidTest
-# run sample instrumented unit test
-  - adb shell am instrument -w -e debug false -e class com.owncloud.android.datamodel.OCFileUnitTest com.owncloud.android.test/android.support.test.runner.AndroidJUnitRunner
-env:
-  global:
-  - secure: h4Y7ZvgbvOj5T71ubRcw3Fy3KXF8qHugRFLGK3q2R9YuRsDAf8XH+Y/UiXyH8sac2QSj7Zlny1kA1DEJgwhTXs9wsAVKVJCQNTJGEvhm/4uQgPeNMzMv07Lqe8V+KUBsFH5qhfPJO357ERW0k2f2qljoLSHtHStclt7iGvFdynA=
-  - secure: o9L6lXWpXowhQSdiUSmajliBUkQ6n7NrBUqhC09lqe7yXSGhEsgGRXqHoT3q2B4uIqGSiLCa9HQbW0dfDQCs+pADmzHIl3zbTViR88TSaIhOiTrqMUUl5iaO++pneZ2TzgU9bbGHbl6Ixjc6iALH2+F7P+RUM6vLTNPcfnCJa3g=
-  - secure: ydxZrS7+1ht3p1tC6DE9W9bjLQGjMkwFBwyhNmcdEM6538kN8ZCBQe7NxSsCrC1nSDBLQ17Cziv0XJHl/pCfPrbkrPPgVFpjDfPeqC2zcGcCNcFQUEylXCvQ4uRU2hKL6dPqCsOQ57Pv3qwpPoprl/usoN5Wh8V7BKplU88ZaYM=
-  matrix:
-  - ANDROID_TARGET=android-23 ANDROID_ABI=armeabi-v7a