Add link to documentation in Readme

[stevehanson]

This update just adds a link to the documentation in the readme so people can find it without having to Google.

[olleolleolle]

Perhaps this is an even better documentation link?

https://www.rubydoc.info/github/ruby-ldap/ruby-net-ldap/master

[stevehanson]

@olleolleolle Good call. I went ahead and updated it. Thanks.

[olleolleolle]

@stevehanson I have thought about this, and came to this: the gemspec can have this metadata, too.

Here's an example from another project, which has defined every metadata field supported by RubyGems:

  s.metadata = {
    "bug_tracker_uri" => "https://github.com/celluloid/celluloid/issues",
    "changelog_uri" => "https://github.com/celluloid/celluloid/blob/master/CHANGES.md",
    "documentation_uri" => "https://www.rubydoc.info/gems/celluloid",
    "homepage_uri" => "https://celluloid.io/",
    "mailing_list_uri" => "http://groups.google.com/group/celluloid-ruby",
    "source_code_uri" => "https://github.com/celluloid/celluloid",
    "wiki_uri" => "https://github.com/celluloid/celluloid/wiki"
}

(documentation_uri is what we're discussing here.)

[HarlemSquirrel]

Thanks but this was taken care of by #318