Some code style fixes. (#33)

Author: judy2k

.gitignore

@@ -1,4 +1,3 @@
-
 # Created by https://www.gitignore.io/api/python
 
 ### Python ###

nexmo/__init__.py

@@ -1,14 +1,22 @@
-__version__ = '1.5.0'
-
-import requests, os, warnings, hashlib, hmac, jwt, time, uuid, sys
-
 from platform import python_version
 
+import hashlib
+import hmac
+import jwt
+import os
+import requests
+import sys
+import time
+from uuid import uuid4
+import warnings
+
 if sys.version_info[0] == 3:
     string_types = (str, bytes)
 else:
     string_types = (unicode, str)
 
+__version__ = '1.5.0'
+
 
 class Error(Exception):
     pass
@@ -257,10 +265,10 @@ def signature(self, params):
         md5.update(self.signature_secret.encode('utf-8'))
         return md5.hexdigest()
 
-    def get(self, host, request_uri, params={}):
+    def get(self, host, request_uri, params=None):
         uri = 'https://' + host + request_uri
 
-        params = dict(params, api_key=self.api_key, api_secret=self.api_secret)
+        params = dict(params or {}, api_key=self.api_key, api_secret=self.api_secret)
 
         return self.parse(host, requests.get(uri, params=params, headers=self.headers))
 
@@ -301,10 +309,10 @@ def parse(self, host, response):
 
             raise ServerError(message)
 
-    def __get(self, request_uri, params={}):
+    def __get(self, request_uri, params=None):
         uri = 'https://' + self.api_host + request_uri
 
-        return self.parse(self.api_host, requests.get(uri, params=params, headers=self.__headers()))
+        return self.parse(self.api_host, requests.get(uri, params=params or {}, headers=self.__headers()))
 
     def __post(self, request_uri, params):
         uri = 'https://' + self.api_host + request_uri
@@ -328,7 +336,7 @@ def __headers(self):
         payload.setdefault('application_id', self.application_id)
         payload.setdefault('iat', iat)
         payload.setdefault('exp', iat + 60)
-        payload.setdefault('jti', str(uuid.uuid4()))
+        payload.setdefault('jti', str(uuid4()))
 
         token = jwt.encode(payload, self.private_key, algorithm='RS256')