Initial commit for _sass.

Props @michaelArestad @hugobeta, and @jacklenox.

* Give prefix to variable files. This avoids confusion with files of similar names like typography. It also helps with the visual recognition over what file does what.
* Set up mixins-master.
* Setting foundation for encouraging in larger projects use of more than one mixing file. This creates a master mixins file that we can then bring subs into if the project grows.
* Fixed line breaks, spacing and new lines. Props @gregrickaby.
* Nest widget select. Props @gregrickaby.
* Make variables be variables-site. Makes this the global variables folder. People can then use sub folders in sections for local only variables.
* Change content directory to be site directory.
* Remove zip. Revert `style.css` to not be auto generated version.
* Fixes rem size issue on body font.
* Fixes for differences between `_s` and `_sass`. Fixed font sizes, added in display block to classes so they compile and the theme check
passes.
* Remove text domain and clean up css.

sass/mixins/_mixins-master.scss

@@ -0,0 +1,36 @@
+// Rem output with px fallback
+@mixin font-size($sizeValue: 1.6) {
+  	font-size: ($sizeValue * 10) + px;
+  	font-size: $sizeValue + rem;
+}
+
+// Box model
+@mixin box-sizing($box-model) {
+  	box-sizing: $box-model;
+  	-moz-box-sizing: $box-model; // Firefox <= 19
+	-webkit-box-sizing: $box-model; // Safari <= 5
+}
+
+// Border radius
+@mixin border-radius($radius) {
+  	background-clip: padding-box;  /* stops bg color from leaking outside the border: */
+  	border-radius: $radius;
+  	-webkit-border-radius: $radius;
+}
+
+// Center block
+@mixin center-block {
+  	display: block;
+  	margin: 0 auto;
+}
+
+// Clearfix
+@mixin clearfix() {
+    content: "";
+    display: table;
+}
+
+// Center after (not all clearfix need this also)
+@mixin clearfix-after() {
+    clear: both;
+}