Allow gitignored Google credentials

I like leaving my Google creds in place, which means I'd constantly
get git telling me about having modified the index.js file.

Require credentials in from a gitignored file.

Add the dashboards directory to gitignore too to prevent accidental
commitage.
Fixed up tab alignment issue.

Reduced the border between tabs to 3px (3+3px = 6px) for each tab!

Ensured that also happens for the selected tab (using margin-right)

Reduced the min width of a tab to 8em.
Remove logging from module stub generation

This is causing an error during deployment:

    Running "shell:generate_module_stubs" (shell) task
    Warning: stdout maxBuffer exceeded.Use --force to continue.

Relevant links from @lennym:

- https://github.com/sindresorhus/grunt-shell/blob/master/tasks/shell.js#L22
- http://nodejs.org/api/child_process.html#child_process_child_process_exec_command_options_callback

Nobody ever sees this non-error logging, so we should just remove it.
Merge pull request #434 from alphagov/bugfix/shrink-tabs

Fixed up tab alignment issue.
Merge pull request #438 from alphagov/remove-logging-module-generation

Remove logging from module stub generation
Merge pull request #433 from alphagov/gitignored-google-config

Allow gitignored Google credentials