use unsigned ints for iteration

src/database.cc

@@ -357,7 +357,7 @@ void Database::TraceCallback(EV_P_ ev_async *w, int revents) {
     AsyncTrace* async = static_cast<AsyncTrace*>(w->data);
 
     std::vector<std::string> queries = async->get();
-    for (int i = 0; i < queries.size(); i++) {
+    for (unsigned int i = 0; i < queries.size(); i++) {
         Local<Value> argv[] = {
             String::NewSymbol("trace"),
             String::New(queries[i].c_str())

src/statement.h

@@ -90,7 +90,7 @@ public:
             callback = Persistent<Function>::New(cb_);
         }
         ~Baton() {
-            for (int i = 0; i < parameters.size(); i++) {
+            for (unsigned int i = 0; i < parameters.size(); i++) {
                 Values::Field* field = parameters[i];
                 DELETE_FIELD(field);
             }