Extend aws region validation (#430)

* allow extra aws region

* add unit test for gov cloud

* matches any pattern between iot and amazonaws

* update to avoid empty string or . in region sub-str

Author: xiazhvera

device/index.js

@@ -512,7 +512,8 @@ function DeviceClient(options) {
       }
 
       if (!isUndefined(options.host) && isUndefined(options.region)) {
-         var pattern = /[a-zA-Z0-9]+\.iot\.([a-z]+-[a-z]+-[0-9]+)\.amazonaws\..+/;
+         // extract anything in between "iot" and "amazonaws" as region
+         var pattern = /[a-zA-Z0-9]+\.iot\.([^\.]+)\.amazonaws\..+/;
          var region = pattern.exec(options.host);
          if (region === null) {
             console.log('Host endpoint is not valid');