Release v2.2.5

• generateToken() now throws when invalid options are passed instead of returning false #62
• Fixes broken session.generateToken() issue due to bad capturing of this #58
• generateToken() now rounds the expireTime option down to a whole number #76
• No longer mutates the options passed into createSession() (#77) or generateToken() (#90).
• Handles 503 server errors #80 (thanks @ametaireau)
• Fixed typo in an error message #81 (thanks @radekk)