Basic wording tweaks

Hi @svenfuchs, as requested over on https://github.com/ruby-conferences/ruby-conferences-site/issues/13, I took a look at the wording here and I do have a couple suggestions.

I've started using RubyConferences.org when referring to the site, so 70edd22 updates that.

Then, 9a0c4e3 removes a second link to that issue and the clause containing it.

Seems like overkill to link to it again and I feel a little called out by the tone of that clause - I hope you'll consider removing it. To be honest with you, I think the section is actually strengthened by removing the third paragraph entirely, but I didn't want to go there in this PR in case you disagreed.

Do whatever you think is best and thanks again for the respectful way you've gone about this! :heart: :heart: :heart:

Jon