Update cla link to remove clahub, since it no longer exists.

Fixes #424.

CONTRIBUTING.md

@@ -1,3 +1,3 @@
 # Contributor License Agreement
 
-To get started, please sign the <a href="https://www.clahub.com/agreements/gittup/tup">Contributor License Agreement</a>.
+If you are plan to making significant changes to tup (ie: something that requires significant re-working of the source code, or a new feature, etc) and want to get them into the main repository, then you'll need to fill out a copyright assignment form. To get started, please sign the <a href="https://gittup.org/tup/icla.txt">Contributor License Agreement</a>.

docs/html/pub/icla.txt

@@ -14,10 +14,8 @@ Contributor as well as the protection of the Author and the users;
 it does not change your rights to use your own Contributions for any
 other purpose.  If you have not already done so, please complete and
 sign, then scan and email a pdf file of this Agreement to
-marfey@gmail.com.  If necessary, send an original signed Agreement to
-Michael Shal, 12136 Wedgeway Pl, Fairfax, VA 22033, U.S.A.  Please
-read this document carefully before signing and keep a copy for your
-records.
+marfey@gmail.com.  Please read this document carefully before signing
+and keep a copy for your records.
 
   Full name: ______________________________________________________