feat(Gruntfile.js): Added package-c task which creates a unified single header css-layout.h for use in C code ;

src/Layout.c

@@ -12,7 +12,10 @@
 #include <stdlib.h>
 #include <string.h>
 
+// in concatenated header, don't include Layout.h it's already at the top
+#ifndef CSS_LAYOUT_IMPLEMENTATION
 #include "Layout.h"
+#endif
 
 #ifdef _MSC_VER
 #include <float.h>