Fixes for #82 and #79

[dairiki]

This adds stub DebugMailer.bind() and DummyMailer.bind() methods. (#82)
Also it fixes pyramid_mailer.debug.includeme(), and pyramid_mailer.testing.includeme() to add the .mailer request property. (#79)

Review welcome.

[mmerickel]

I guess this should be called for the default Mailer as well, no?

[dairiki]

Maybe. Right now Mailer.bind does its own equivalent checks, so the call would be redundant. (Those checks are intertwingled with the extraction of the pertinent parameters.)

Another way to go, which I considered initially, would be to have a common _extract_bind_options that gets called by all three .bind methods which does both the check and the extraction of the default_sender and transaction_manager options. (The extracted parameters would then be ignored by everyone except Mailer.bind.) The ugliness with doing that has to do with the way the default values for these options is determined: in the real Mailer, defaults for these come from object properties; in the dummy/debug mailers, these parameters, ignored as they are, have indeterminate (or inconsequential) default values. (If that makes any sense...)

[mmerickel]

I think I would argue that for consistency you should call _check_bind_options from Mailer.bind and separate the checking from the popping.

[dairiki]

(Done.)

[dairiki]

Should this be named with an underscore (_set_mailer) to emphasize that it is not published API?

[mmerickel]

That's fine if you want. Alternatively it could be a full-blown config.set_mailer directive, but we can save that for later so maybe _set_mailer for now.

[mmerickel]

LGTM, thank you @dairiki.