Python 3 support (#755)

* Python 3 support

* Fix import_vs_environment in xenia-build

* Drop support for Python 2

* Fix CIs and xb.bat

* Require Python3.4+ because of Ubuntu Trusty

* popen.communicate returns bytes instead of string

* Useful info in travis

* universal_newlines should be True

* Changed shebang to python 3

* Python 3 shebang fix

* Clang python 3 shebang fix

.travis.yml

@@ -33,6 +33,7 @@ addons:
       - clang-3.8
       - clang-format-3.8
       - libc++-dev
+      - python3
 
 git:
   # We handle submodules ourselves in xenia-build setup.
@@ -43,6 +44,7 @@ before_script:
   - export CC=clang-3.8
   # Dump useful info.
   - $CXX --version
+  - python3 --version
   # Prepare environment (pull dependencies, build tools).
   - travis_retry ./xenia-build setup