Add instructions for local development

Just opening the `file:///path/to/repo/index.html` file in a browser doesn't work as expected, you need a basic web server to serve the static content.
Flatten mean/percentiles based on few submissions.
Add a preference for "flatten noisy lines"
Merge pull request #21 from mreid-moz/flatten_noisy_lines

Flatten mean/percentiles based on few submissions.
Update ANR dashboard
Merge pull request #22 from darchons/master

Update ANR dashboard