Return raw value of template literal even if it is an empty string.

This clarifies the API a bit. Let function callee decide how to define
an empty string.

Author: beefancohen

src/util/buildTemplateLiteral.js

@@ -28,7 +28,7 @@ const buildTemplateLiteral = templateLiteral => {
     return raw;
   }, '');
 
-  return rawString === '' ? undefined : rawString;
+  return rawString;
 };
 
 export default buildTemplateLiteral;