Remove the "PreferBufferedTransport" flag

[AnthonySteele]

Summarise the changes this Pull Request makes.

The "PreferBufferedTransport" flag should always be true. In Version 4.0 we are are removing redundant code paths because

• we can make breaking changes (although the majority of the consumers should be able to just recompile and carry on)
• and these "experiments" can be productionised now. We keep the best/fastest path and drop the rest. The new code is ether ready for mainstream use, or should be made so.

So should the StatsDPublisher with an IStatsDPublisher _inner also go?
And the distinction between IStatsDTransport and IStatsDBufferedTransport ?

Please include a reference to a GitHub issue if appropriate.

[martincostello]

Have added some musing on the above in #118.

[martincostello]

So do you reckon this is ready to merge as-is, then I'll rebase #118 and merge that?

We can then do any allocation-savings once we've consolidated things a bit.

[AnthonySteele]

If you want, we can merge this as is, and then consolidate after.
That bool option PreferBufferedTransport should go and the code should assume the true path, one way or the other.