Correct link syntax in README.md (NagiosEnterprises#512)

* Correct Markdown link syntax in README.md

Commit 70d4b0b imported a new version of README.md, but the syntax of
the links for Markdown was wrong:

    http://example.com/[Link text]

The correct syntax in Markdown is:

    [Link text](http://example.com/)

This commit corrects the syntax of 10 such instances.

* Add self to THANKS per @hedenface's request

README.md

@@ -15,7 +15,7 @@ Visit the Nagios homepage at https://www.nagios.org for documentation,
 new releases, bug reports, information on discussion forums, and more.
 
 
-https://www.nagios.org/about/features/[Features]
+[Features](https://www.nagios.org/about/features/)
 -----------------------------------------------
 * Monitoring of network services (via SMTP, POP3, HTTP, PING, etc).
 * Monitoring of host resources (processor load, disk usage, etc.).
@@ -35,9 +35,9 @@ https://www.nagios.org/about/features/[Features]
 Changes
 -------
 See the
-https://raw.githubusercontent.com/NagiosEnterprises/nagioscore/master/Changelog[Changelog]
+[Changelog](https://raw.githubusercontent.com/NagiosEnterprises/nagioscore/master/Changelog)
 for a summary of important changes and fixes, or the
-https://github.com/NagiosEnterprises/nagioscore/commits/master[commit history]
+[commit history](https://github.com/NagiosEnterprises/nagioscore/commits/master)
 for more detail.
 
 
@@ -48,30 +48,28 @@ Latest releases can be downloaded from https://www.nagios.org/download/
 
 Installation
 ------------
-http://nagios.sourceforge.net/docs/nagioscore/4/en/quickstart.html[Quickstart installation guides]
+[Quickstart installation guides](http://nagios.sourceforge.net/docs/nagioscore/4/en/quickstart.html)
 are available to help you get Nagios up and monitoring.
 
 
 Documentation & Support
 -----------------------
-* http://nagios.sourceforge.net/docs/nagioscore/4/en/[User Guide]
-* https://library.nagios.com/library/products/nagioscore/[Nagios Core Documentation Library]
-* https://support.nagios.com/forum/viewforum.php?f=7[Support Forums]
-* https://www.nagios.org/support/[Additional Support Resources]
+* [User Guide](http://nagios.sourceforge.net/docs/nagioscore/4/en/)
+* [Nagios Core Documentation Library](https://library.nagios.com/library/products/nagioscore/)
+* [Support Forums](https://support.nagios.com/forum/viewforum.php?f=7)
+* [Additional Support Resources](https://www.nagios.org/support/)
 
 
 Contributing
 ------------
 The Nagios source code is hosted on GitHub:
 https://github.com/NagiosEnterprises/nagioscore
 
-Do you have an idea or feature request to make Nagios better? Join or
-start a discussion on the
-https://support.nagios.com/forum/viewforum.php?f=34[Nagios Core Development forum].
-Bugs can be reported by
-https://github.com/NagiosEnterprises/nagioscore/issues/new[opening an
-issue on GitHub]. If you have identified a security related issue in
-Nagios, please contact [email protected].
+Do you have an idea or feature request to make Nagios better? Join or start a
+discussion on the [Nagios Core Development forum](https://support.nagios.com/forum/viewforum.php?f=34).
+Bugs can be reported by [opening an issue on GitHub](https://github.com/NagiosEnterprises/nagioscore/issues/new).
+If you have identified a security related issue in Nagios, please contact
+[email protected].
 
 Patches and GitHub pull requests are welcome. Pull requests on GitHub
 link commits in version control to review and discussion of the
@@ -81,5 +79,5 @@ who was involved.
 Created by Ethan Galstad, the success of Nagios has been due to the
 fantastic community members that support it and provide bug reports,
 patches, and great ideas. See the
-https://raw.githubusercontent.com/NagiosEnterprises/nagioscore/master/THANKS[THANKS file]
+[THANKS file](https://raw.githubusercontent.com/NagiosEnterprises/nagioscore/master/THANKS)
 for some of the many who have contributed since 1999.

THANKS

@@ -322,6 +322,7 @@ wrong, please let me know.
 * Todd Wheeler
 * Tom Bertelson
 * Tom De Blende
+* Tom Ryder
 * Tom Welsh
 * Tomer Okavi
 * Ton Voon