Document how samples should be run and deployed about dart-samples

I'd be glad to have this assigned to me. For starters I'll add a few lines to README.md with step-by-step instructions for using the Dart Editor to run and deploy the samples from the downloaded zip file.

Below is a rough outline. If this is what you had in mind please comment and I'll submit a polished version as a pull request.

To build these samples in the Dart Editor
1. download the zip
2. select new project from existing file
3. right click dart_io_mini_samples/pubspec.yaml and select pub build (wait for the progress bar)
4. right click html5/pubspec.yaml and select pub build (wait for the progress bar)
5. right click io/*.dart and select run (watch the command line output)
6. right click html5 samples and select run in dartium (dartium browser opens)

To run the io_mini tests
+ Windows users download git-scm and use Git Bash
+ cd ../dart_io_mini_samples
+ ./runtests.sh

To run the html5 tests
1. configure launch
2. working directory ../html5
3. script arguments 'analyze_libs'
4. uncheck Run in checked mode
5. click apply, click run