Remove 'highly' from README intro

Author: bskinn

README.md

@@ -27,7 +27,7 @@
 
 `sphobjinv` (short for '**sph**inx **obj**ects.**inv**') can help!
 
-The syntax required for a functional Sphinx cross-reference is highly
+The syntax required for a functional Sphinx cross-reference is
 non-obvious in many cases. Sometimes Sphinx can guess correctly what
 you mean, but it's pretty hit-or-miss.  The best approach is to provide
 Sphinx with a completely specified cross-reference, and that's where