Added readme info

Author: NiallSmyth

README.md

@@ -1,2 +1,22 @@
 # Custard.SassC
 A custard command for compiling SCSS into CSS using SassC
+
+Usage:
+  compile:scss [options] <input> <output>
+
+Arguments:
+  input                          File or directory to compile
+  output                         File or directory to output to
+
+Options:
+  -s, --style=STYLE              Output style. Can be: nested, compressed. [default: "compressed"]
+  -l, --line-numbers             Emit comments showing original line numbers.
+  -i, --import-path=IMPORT-PATH  Set Sass import path.
+  -m, --sourcemap                Emit source map.
+  -M, --omit-map-comment         Omits the source map url comment.
+  -p, --precision=PRECISION      Set the precision for numbers.
+  -a, --autoprefix               Run postcss autoprefixer on output CSS files.
+  -vv                            Increase output verbosity (displays output from sasscb and autoprefixer).
+
+**Note:** The autoprefixer option requires postcss CLI and autoprefixer to be installed globally. 
+These are node.js modules and can be installed