Rationalised grey and pink tints according to document from Design.
Updated use cases where palette colour names have changed.
Corrected over-zealous find & replace.
Merge pull request #48 from Financial-Times/rationalise-greys-and-pink-tints

Rationalised grey and pink tints according to document from Design.

DESIGN NOTE
Prev / next button loses its current colour as **cool-grey2** is deprecated and will soon be obsolete. Hence a replacement colour was needed. Looking at the new colours outlined by Dan Skinner [March 2013] ORG003 Proposed greys.psd

Replacement colours
normal state = white
hover state =  grey-tint1

This matches as close as possible to current FT.com slideshow styling