Add fluent interface for constructing a parser configuration.

[Nemec]

Instead of configuring the parser via attributes, it would be useful to be able to programmatically build the parser with a fluent interface. This will allow options to be added and removed dynamically and provide a code (instead of configuration) based interface for parsing.

There is some work already started on this (see clipr.Fluent namespace) but it's still in alpha stage.