Closes #159, #149. Update prettydiff to fix LESS and SCSS.

- SCSS Interpolated text variables
- LESS &:extend

examples/simple-jsbeautifyrc/sass/expected/interpolated-text-vars.scss

@@ -0,0 +1,8 @@
+@mixin text-emphasis-variant($parent, $color) {
+  #{$parent;} {
+    color: $color;
+  }
+  a#{$parent;}:hover {
+    color: darken($color, 10%);
+  }
+}

examples/simple-jsbeautifyrc/sass/original/interpolated-text-vars.scss

@@ -0,0 +1,8 @@
+@mixin text-emphasis-variant($parent, $color) {
+  #{$parent} {
+    color: $color;
+  }
+  a#{$parent}:hover {
+    color: darken($color, 10%);
+  }
+}

package.json

@@ -94,7 +94,7 @@
     "lodash": "2.4.1",
     "loophole": "^1.0.0",
     "node-uuid": "^1.4.1",
-    "prettydiff": "^1.6.11",
+    "prettydiff": "^1.6.12",
     "space-pen": "^4.3.0",
     "strip-json-comments": "^0.1.3",
     "temp": "^0.8.0",