Bump gulp-cache to 0.2

Changelog available here:
https://github.com/jgable/gulp-cache/compare/3b44956e60b4a96905ade5391f730f03604ae27c...0.2.0
Merge pull request #177 from google/gulp-cache-bump

Bump gulp-cache to 0.2
Fixes #174 - moves demo classes to styleguide
Move demo gray to sass utils
Merge pull request #178 from google/grids

Fixes #174 - moves demo classes to styleguide
Fix missing pygments highlighting
Strip unnecessary link in styleguide
Close GH-171: Livereload breaks on jshint error(s) when running `gulp serve`. Fixes #169
gulpfile - don't need `init` anymore
Give serve preference to files in .tmp

From my testing, the browserSync server prefers files in app over files in .tmp when they have the same name. .tmp files should be preferred, since any file in .tmp has been processed in some way (e.g., a main.css file that's autoprefixed into .tmp, or an index.html that contains some templating that's precompiled into .tmp).
Merge pull request #185 from robwierzbowski/patch-2

Give server preference to files in .tmp
Removed reference to BrowserSync running instance
Merge pull request #189 from shakyShane/master

Removed reference to BrowserSync running instance
readme - link to latest release
update ignore list