Add circleci config with mac, windows and linux testing (#338)

- Add EMSDK_NOTTY variable which we can use on CI to prevent tty output.
- Add test.bat for windows which mirrors test.sh.
- Remove travis support

test.bat

@@ -0,0 +1,6 @@
+:: equivilent of test.sh as windows bat file
+set PATH=%PATH%;%PYTHON_BIN%
+@CALL emsdk install latest
+@CALL emsdk activate latest
+@CALL emsdk_env.bat --build=Release
+@CALL emcc.bat -v