Add some details to README.txt for people new to mercurial (like I am)

Author: tinkster

README.txt

@@ -1 +1,22 @@
-The WebId mercurial repo
+The WebID Mercurial Repo
+========================
+
+  All Invited Experts should have access to it. This should be a good
+  place to edit the spec before we push it to svn, to put test cases,
+  and other code.
+        
+        $ hg clone https://dvcs.w3.org/hg/WebID
+        $ cd WebID
+	$ echo "[ui]" >>.hg/hgrc
+	$ echo "username=${W3C_USERNAME}" >>.hg/hgrc
+        
+        # edit files
+        
+        $ hg add ${newfiles}
+        $ hg commit
+        $ hg push
+
+        $ hg pull
+        
+  Use your W3C username and password.
+