fix($http): send GET requests by default

Fixes #5985
Closes #6401

src/ng/http.js

@@ -664,6 +664,7 @@ function $HttpProvider() {
      */
     function $http(requestConfig) {
       var config = {
+        method: 'get',
         transformRequest: defaults.transformRequest,
         transformResponse: defaults.transformResponse
       };