Sass: Introducing variables.sass file.

For Blender Cloud specific variables.

src/styles/_variables.sass

@@ -0,0 +1 @@
+$color-bg-dark-pages: #151515

src/styles/main.sass

@@ -83,9 +83,6 @@
 @import "../../../pillar/src/styles/_project-dashboard"
 @import "../../../pillar/src/styles/_user"
 
-@import _welcome
-@import _services
-@import _about
 @import "../../../pillar/src/styles/_search"
 @import "../../../pillar/src/styles/_organizations"
 
@@ -97,3 +94,9 @@
 @import "../../../pillar/src/styles/plugins/_js_select2"
 
 /* CSS for pillar-font comes from fontello.com using static/assets/font/config.json */
+
+@import variables
+@import welcome
+@import services
+@import about
+@import list_films