Documentation and validation work

[GlenTiki]

Currently, the documentation doesn't show how to customise the headers on the request.

For the duration option, browsing the code, it is required, but never checked, @mcollina, should we put a check in for the duration and test it, or default it to some value, eg. 10? Obviously, this will need a unit test and documentation work, too.

Supported HTTP methods should be documented.

Show the default value for the http pipelining value.

Update the .track doc, I left outputStream listed as a param name when I should have listed opts.

[mcollina]

Go ahead with doc and validations.

[mcollina]

IMHO connections and duration should always be specified, but Dave would like to have defaults