Closes#1233
- Handle path-separators properly. Use "path.sep" instead of "/".
Or use "require.resolve()" if possible
- Use "execFile" instead of "exec" to run the Handlebars executable.
This prevents problems due to (missing) shell escaping.
- Use explicit call to "node" in order to run the executable on Windows.
- Add "appveyor"-CI in order to run regular tests on Windows.