only check for BOM at the start of the line

Looking in general causes false positives, see #550

Author: steveklabnik

tidy.sh

@@ -1,3 +1,3 @@
-git grep -l $'\xEF\xBB\xBF' .
+git grep -l $'^\xEF\xBB\xBF' .
 
 if [ $? -eq 0 ]; then exit 1; else exit 0; fi