Add some test cases and run test cases on binding/render dir (#1168)

* Travis run test cases on binding and render dir and add some test cases for binding and render

coverage.sh

@@ -0,0 +1,13 @@
+#!/usr/bin/env bash
+
+set -e
+
+echo "mode: count" > coverage.out
+
+for d in $(go list ./... | grep -E 'gin$|binding$|render$'); do
+    go test -v -covermode=count -coverprofile=profile.out $d
+    if [ -f profile.out ]; then
+        cat profile.out | grep -v "mode:" >> coverage.out
+        rm profile.out
+    fi
+done