Add readability-redundant-* checks

There's a number of redundancies in our code that clang can sanitize
out.  Fix the existing problems, and enable the checks.

Signed-off-by: Ed Tanous <edtanous@google.com>
Change-Id: Ie63d7b7f0777b702fbf1b23a24e1bed7b4f5183b
diff --git a/http/app.hpp b/http/app.hpp
index 03de3f8..c1472e5 100644
--- a/http/app.hpp
+++ b/http/app.hpp
@@ -142,7 +142,7 @@
 
     std::vector<const std::string*> getRoutes()
     {
-        const std::string root("");
+        const std::string root;
         return router.getRoutes(root);
     }
     std::vector<const std::string*> getRoutes(const std::string& parent)