Update grunt-sass to 0.18.0

[netweb]

Upstream changes:

• grunt-sass: ​https://github.com/sindresorhus/grunt-sass/compare/v0.16.0...v0.18.0
• node-sass: ​https://github.com/sass/node-sass/compare/v1.0.3...v2.0.0
  • Node v2.0: Release notes: ​https://github.com/sass/node-sass/releases/tag/v2.0.0
  • libsass v3.1: Release notes ​https://github.com/sass/libsass/releases/tag/3.1.0
  • node.js v0.12 (stable) support (while keeping the v0.10 compatibility)
    • NodeJS v0.12 (stable) released 6th Feb 2015 ​http://blog.nodejs.org/2015/02/06/node-v0-12-0-stable/

---

With the changes in _admin.scss in the included patch there is no difference to any file in /build folder after running grunt build or grunt precommit.

The addition of the leading zero is due to the upstream issue in ​libsass/issues/623, this is fixed as part of libsass v3.1.

Without the changes all the colors.css files (MP6) result in changes for each e.g:

build/wp-admin/css/colors/sunrise/colors.css

@@ -218 +218 @@
 
 #wpadminbar #adminbarsearch .adminbar-input::-webkit-input-placeholder {
   color: #fff;
-  opacity: .7; }
+  opacity: 0.7; }

[netweb]

In 31343.1.diff​ refreshed against latest /trunk

To reiterate, no changes to the /build folder after running grunt or /src after grunt precommit

[wonderboymusic]

In 31648:

Update grunt-sass to 0.18.0.

Props netweb.
Fixes #31343.