Default Travis builds to Python3

Author: AndreMiras

.travis.yml

@@ -31,5 +31,5 @@ before_script:
   - tox
 
 script:
-  - docker build --tag=p4a --file Dockerfile.py2 .
+  - docker build --tag=p4a --file Dockerfile.py3 .
   - docker run p4a /bin/sh -c "$COMMAND"

Dockerfile.py2

@@ -3,13 +3,13 @@
 #   - python-for-android dependencies
 #
 # Build with:
-#     docker build --tag=p4a --file Dockerfile.py2 .
+#     docker build --tag=p4apy2 --file Dockerfile.py2 .
 #
 # Run with:
-#     docker run -it --rm p4a /bin/sh -c '. venv/bin/activate && p4a apk --help'
+#     docker run -it --rm p4apy2 /bin/sh -c '. venv/bin/activate && p4a apk --help'
 #
 # Or for interactive shell:
-#     docker run -it --rm p4a
+#     docker run -it --rm p4apy2
 #
 # Note:
 #     Use 'docker run' without '--rm' flag for keeping the container and use

Dockerfile.py3

@@ -3,13 +3,13 @@
 #   - python-for-android dependencies
 #
 # Build with:
-#     docker build --tag=p4apy3 .
+#     docker build --tag=p4a --file Dockerfile.py3 .
 #
 # Run with:
 #     docker run -it --rm p4apy3 /bin/sh -c '. venv/bin/activate && p4a apk --help'
 #
 # Or for interactive shell:
-#     docker run -it --rm p4apy3
+#     docker run -it --rm p4a
 #
 # Note:
 #     Use 'docker run' without '--rm' flag for keeping the container and use