Add SignedJWT support and Reseller API sample to Perl Client Library.

[richieforeman]

This PR adds OAuth2 Signed JWT (Service Accounts) support to the library.

Summary:

• Add JSON::WebToken as a dependency.
• Add Reseller API sample to '/eg/service_accounts/reseller.pl'
• Add 'Google::API::OAuth2::SignedJWT' class.
• Shamelessly add myself (and email address) to Authors file.

[captin411]

Does the META.json also need reference to JSON::WebToken as a requirement or does the build process figure it out from cpanfile?

[richieforeman]

I must be transparent and admit that my Perl skills are a bit weak. I manually added the requirement to the cpanfile. I would imagine that 'META.json' would also need it -- I can get this PR patched up.

[comewalk]

@richieforeman Thank you for your contribution! It looks good to me. I'm ready for merging your PR and pushing to CPAN. Please wait for a while.

@captin411 Thank you for your comment. As a mention for #15 (comment), I use Dist::Milla for building this CPAN module. META.json will be updated through build process, I think. I'll update related files after merging this PR.

Thanks!

[captin411]

During testing, we did find a separate bug. I will create a separate branch with test cases and patch

[comewalk]

@richieforeman just merged! thanks!

[comewalk]

@captin411 Thank you! Please feel free send a PR 😄