Introduce the option to hide special buffers

Some "boring" buffers can now optionally be hidden by
the users via the use of the `nrepl-hide-special-buffers` setting.
By default all special buffers are visible.

Conflicts:

	CHANGELOG.md
	nrepl.el
	test/nrepl-tests.el
Introduce the option to hide special buffers

Some "boring" buffers can now optionally be hidden by
the users via the use of the `nrepl-hide-special-buffers` setting.
By default all special buffers are visible.

Conflicts:

	CHANGELOG.md
	nrepl.el
	test/nrepl-tests.el