including a necessary header file

Aaron Leung · Aaron Leung · commit 63930f80f63e · 2014-06-02T11:18:25.000-07:00
diff --git a/utf8_string.cpp b/utf8_string.cpp
@@ -2,6 +2,7 @@
 #define SASS_UTF8_STRING
 
 #include <string>
+#include <cmath>
 
 namespace Sass {
   namespace UTF_8 {
