Don't format _deps dir. (#306)

The _deps dir is generated by cmake, under the build dir.
In the case where a separate build dir is not being used,
don't format _deps.

Author: jhferris

tools/format.sh

@@ -44,7 +44,7 @@ while [[ "$1" != "" ]]; do
     shift
 done
 
-FIND="find . -name .git -prune -o -name .build -prune -o"
+FIND="find . -name .git -prune -o -name _deps -prune -o -name .build -prune -o"
 
 if [[ "$sed_check" == "y" ]]; then
   # Correct common miscapitalizations.