Bumps [yard](https://github.com/lsegal/yard) from 0.8.7.2 to 0.9.20.
- [Release notes](https://github.com/lsegal/yard/releases)
- [Changelog](https://github.com/lsegal/yard/blob/master/CHANGELOG.md)
- [Commits](https://github.com/lsegal/yard/compare/v0.8.7.2...v0.9.20

)
Signed-off-by: dependabot[bot] <support@github.com>

require whole "grocer" gem

otherwise you won't load "lib/grocer.rb"
and you'll see "NoMethodError (undefined method `pusher' for Grocer:Module):" error.

Pull out pusher into separate method

Fix generator

The generator for initializer.rb was calling passbook.p12_cert and the correct method name is p12_certificate

Push notification passphrase

Add an optional config field to set the passphrase for
push notification certificate. Grocer makes it optional.

Add spec for it, update readme with instructions. Increased patch
version.

Corrected some mistakes in readme

fixing a small style nit

adding in link to blog post on 0.4.0 release

Adding in support for multiple certificates on signatures and updating documentation.

updating travis with the lastest versions of Ruby

Made grocer version minimum required for passbook notifs

Grocer added passbook notifications for 0.3.0
https://github.com/grocer/grocer/commit/6d926ad9e7c5b7d03e5ca2b228bef4db640bc3db

tiny typo in readme: congigure -> configure

Upping the rev of the gem to fix problems with older versions of rubyzip