Build testapp_python2 using setup_testapp_python2.py

Has the following requirements:
sdl2,pyjnius,kivy,python2
refs kivy#1263

.travis.yml

@@ -11,4 +11,4 @@ before_install:
 script:
   - docker run p4a /bin/sh -c 'uname -a'
   - docker run p4a /bin/sh -c '. venv/bin/activate && p4a apk --help'
-  - docker run p4a /bin/sh -c '. venv/bin/activate && p4a apk --private testapps/testapp/ --package=com.github.kivy --name "Testapp" --version 0.1 --sdk_dir /opt/android/android-sdk/ --android_api 19 --ndk_dir /opt/android/android-ndk/ --ndk-version 16b --bootstrap=sdl2 --requirements=python2,kivy'
+  - docker run p4a /bin/sh -c '. venv/bin/activate && cd testapps/ && python setup_testapp_python2.py apk --sdk-dir /opt/android/android-sdk --ndk-dir /opt/android/android-ndk'