Added a simple Whitehall namespace and initialiser.  Added a helper for initialising scripts and translating params from ruby to javascript.
Re-wrote javascript section of styleguide. Added a tentative point on CSS.
Styleguide better describes js helpers.

Description of javascript helpers implied that they all would be loaded on every page.  Instead, the definition should include scripts which are reused across multiple views.
Updated styleguide js section & initialisers.

• Singletons are OK too.
• Added note about using strict.
• Use GOVUK namespace for everything.

Also updated GOVUK.init to properly handle singleton initialisation.
JavascriptHelper.initialise_script raws output

params passed to initialise script were being escaped. This
fixes that.
Upgrade slimmer to version 3.22.0