Update documentation to point to GitHub

Greetings! This pull request contributes an update for the CL-WebDAV documentation, updating the source repository link so that it will now denote your CL-WebDAV repository, here at GitHub

The second change in this pull request corrects a revision that was made, evidently, by the GitHub web-based editor interface. When I updated the link in the first change, it seems that the web-editor had somewhat mangled the character encoding. The effect of the second change is to use portable HTML character entities, in encoding the modified text.

If I may introduce my interest in creating a fork of CL-WebDAV: I've begun to evaluate CL-WebDAV in the interest of developing a small server for prototyping a custom synchronization server for the iPad diagram/drawing app, [Omnigraffle](http://www.omnigroup.com/products/omnigraffle-ipad/), as well as for the [iPhone](http://www.omnigroup.com/products/omnifocus-iphone)  and [iPad](http://www.omnigroup.com/products/omnifocus-ipad/) editions of the related Omnifocus task management app (Frankly, at present, I don''t have copies of Omni's OmniPlan or OmniOutliner apps, but I have been making extensive use of those other two)

Granted, I'm not presently familiar with the details of those Omni apps' exacting use of WebDAV. I'd simply noticed that they can be configured to access a custom WebDAV server, as may be available over a local wireless network. So, I thought that a bit of reflective engineering could be appropriate, more than to bother the Omni developers, as yet, in regards to the details of the synchronization protocols used in those apps. I thought that that testing would be easiest to perform, with a WebDAV server in Common Lisp, and thusly I found CL-WebDAV.

Pending a successful testing session, this evening, I would be interested in your advice towards contributing further pull requests to CL-WebDAV, as for purposes of:

* Class 2 locking support for CL-WebDAV

* a protocol for transforming non-file resources into WebDAV response objects - such that that protocol may integrate with a _portable serialization) layer, such that would  rely on: existing work, such as in 
    * the free/open source Common Lisp software community, cf. [the CLiki index for _serialization_ projects](http://www.cliki.net/serialization) 
    * and the  commercial Common Lisp software community, cf.  [Franz' AllegroCache](http://www.franz.com/products/allegrocache/)


I should hope to be able to complete those contributions, by the time of the end of this year. Presently and frankly, as my being lately again a college student, I'm still adjusting to my college course schedule for the semester. However, I think that I should be able to complete those contributions, within that frame of time. Frankly and personally, so far as I may be able to synchronize with those Omni apps, on the desktop, I think that it may serve to help in keeping my class notes, grocery shopping list, and task items synchronized between my mobile devices and my Linux desktop. (I think, it could also be extended for integrating OmniFocus with Eclipse Mylyn, whether via HTTP or via CORBA)

In addition to contributing to CL-WebDAV, I also hope to develop some further desktop support for Omnifocus's task items, task projects, and calendar integration, and for the Omnigraffle diagram/drawing format, using CLIM. Altogether, I think that it could be to the development of a concept of a personal informatino management portal, of some kind, on the Common Lisp platform - as in regards to, as a student, providing support for managing one's homework, and otherwise for managing one's projects and other tasks lists, with an integrated interface via Common Lisp, on the desktop. 

I had originally located CL-WebDAV via the CLiki. Then, after having found the GitHub repository for the project,  I forked the GitHub repository and  made this short patch - now submitted in the interest of that developers may be able to find the primary CL-WebDAV source code repository, directly, here at GitHub. I hope that my brief introduction in the previous may also be to your interests and your good cheer.

With goodwill,

-- Sean