Formatters can have more than one capitals in there name and SSHKit::Formatter.Dot prints out dots.

This includes two fixes, Fix #74 and Fix #75.

Fix #74 allow `:BlackHole` or `:blackhole` to be passed in as a format. Any future formatters will also benefit, for example in case someone wants to make an `:XML` format.

Fix #75 Dot formatter prints dots. The comparison was well intentioned but the order in which the arguments were placed caused a problem. A full explanation available at Fix #75.