Fix issues in hello-world doc

[bpringe]

Fixed some typos and changed "query string" to "URI path" in one place to be more accurate.

I went through some of the guides recently and took some notes for improvements. I'll submit PRs for other docs once/if this one gets merged.

[hlship]

Thank you for contributing to Pedestal!

Sorry it's taken us such a long time to get around to addressing your Pull Request. We'd like to review and integrate your contribution into the project, but in order to do so we need to ensure that you have signed the Contributor Agreement.

Please find instructions on how to sign the agreement, along with an explanation of why it is important to do so, here:

http://pedestal.io/community/contributing#_contributors_agreement

Thanks!

[bpringe]

Hey @hlship.

I believe I've signed the contributor agreement in the past. Do I need to sign it again?

Also, did you mean to close this PR?

[bpringe]

I signed the contributor agreement (maybe for a second time) anyway. Let me know if you need anything else.

[hlship]

Thanks for your efforts; I'm afraid that the documentation for Pedestal has moved into the main Pedestal repository.