Updates print and open file statements for Python3 compatibility.

Replaces print statement as print() and replaces file() with open() to resolve error occurred when running the `tools/build-ios.sh` script under Python 3 environment.

Signed-off-by: Olli Wang <olliwang@ollix.com>
Merge pull request #80 from olliwang/python3

Update print and open file statements for Python3 compatibility.