Converted to grunt-based build.

Added and configured:
- grunt-dojo
- grunt-contrib-imagemin
- grunt-newer
- grunt-processhtml
- grunt-contrib-clean
- grunt-contrib-copy

Closes #17.

This provides an example for https://github.com/agrc/AGRCJavaScriptProjectBoilerPlate/issues/33.
Merge pull request #35 from agrc/grunt-build

Converted to grunt-based build.