v0.9.0 release

• Added capability to send email notification to existing jobs
• Removed warnings from client.rb
• Refactored and improved exception handling
• A bug is fixed in client which allows only the valid params as options.
  Credit: @Niarfe
• Added a timeout parameter for waiting for jenkins to become ready.
  Credit: @Niarfe
• Added function to reload jenkins. Credit: @missedone
• Fixed a bug where jenkins_path was missing in get_config and post_config.
  Credit: @cylol
• Added capability to obtain jenkins version and other useful information
• Added new tests for various cases, and other code improvements