Validate index.html

- Character encoding
- Can't have a closing link tag (my bad)
- Script tag outside body (paging @easternbloc)
Merge pull request #10 from alphagov/bugfix-validate-index-html

Validate index.html
Include gulp-connect for development

Run `gulp connect` to get a webserver up and running.

I'm not sure how best to make this work with the watch task. For now,
you can just run both tasks.
Show dashboard slug on dashboard

To show how the dev mode works.