LogglyClient documentation suggestion

[alexsaare]

Just a suggestion for the documentation in the readme - please correct me if i'm wrong.

From looking at the code for LogglyClient it would make sense for it to be stored and used as a singleton - especially when using Https transport in a web application environment. The default constructor uses the TransportFactory method which returns a new instance of HttpMessageTransport. This in turn creates a new HttpClient which (as per the official documents) is "intended to be instantiated once and reused throughout the life of an application"