consider renaming the project

Reasons:

• sseserver is very generic, and doesn't imply any of the nice functionality (namespacing support and fast performance) in this library.
• sseserver can be confusing to spell, due to the overlapping collision (s[se)rver].
• sseserver.Server stutters, a no-no in Go best practices.

I am actively interested in improving this code again (and making some decent strides in the develop branch which will eventually be cleaned up and squashed towards a v1.1), and with the proliferation of HTTP/2, SSE may see a resurgence of interest (hence my work on cleanups and the API currently). So if I'm going to rename the project, it should probably be done sooner rather than later, since that's easier when not many people are using it.