Update to t/cover.

t/cover

@@ -5,12 +5,10 @@ set -e
 rm -rf coverage
 
 count=1;
-for file in $(find t -name \*.t.js); do
-  node_modules/.bin/istanbul cover -x 't/**' $file > /dev/null 2>&1
-  if [ -e coverage/coverage.json ]; then
-    mv coverage/coverage.json coverage/coverage$count.json
-    count=$(expr $count + 1)
-  fi
+for file in $(find . ! -path '*/node_modules/*' -name \*.t.js); do
+  node_modules/.bin/istanbul cover -x 't/**' -x '*/t/**' $file > /dev/null 2>&1
+  mv coverage/coverage.json coverage/coverage$count.json
+  count=$(expr $count + 1)
 done
 
 node_modules/.bin/istanbul cover -x 't/**' t/fixtures/echo-1.js > /dev/null 2>&1