Add chrome dart unit tests

Just enough test harness in before adding all the unit tests. 

`bin/setup_app.dart` will build apps in the `app` directory.

Usage:

```
–(~/dart/gen_tools.dart)–($ dart bin/setup_app.dart 
FormatException: This script requires at least 2 positional argument(s), but received 0.

Copies and builds a chrome application or extension

Usage:

dart setup_app.dart [options] <DIRECTORY> <MAIN>

Options:

-h, --help    Print this usage information.

Examples:

dart setup_app.dart app/test_ext harness.dart # Copies the packages folder to "app/test_ext" and builds "harness.dart"
```

Example:

```
dart setup_app.dart app/test_ext harness.dart
```

`bin/load_app.sh` will launch the apps in the `app` directory in either chrome/canary/dartium for mac only. 

Usage: 

```
NOTE: For extensions to be loaded by this script chrome//flags needs 'Experimental Extension APIs' enabled. 
Usage: ./bin/load_app.sh [chrome|canary|dartium] [app/extension directory]
```

Example:

```
./bin/load_app.sh dartium app/test_app/
```

Debated if the `load_app.sh` should just call the build everytime. Both the `test_app` and `test_ext` harness have a reload build it when the `r` key is pressed while open. Before going forward should we get this working in an automated or headless fashion like the spark project?