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.sh

@@ -1,7 +1,11 @@
-#!/usr/bin/env sh
+#!/usr/bin/env bash
+
 echo "test the standard workflow (as close as possible to how a user would do it, in the shell)"
+
+set -x
+set -e
+
 ./emsdk install latest
 ./emsdk activate latest
 source ./emsdk_env.sh --build=Release
 emcc -v
-