Add GitHub links for most of the contributors

CHANGES.txt

 Revision 3.3.5 (2013-08-31):
 
     - Highlight 'import', 'from' and 'as' as include statements.
-      Patch by pydave at GitHub.
+      Patch by David Briscoe
     - Added new option 'python_highlight_file_headers_as_comments' (disabled by
       default) to highlight shebang and coding file headers as comments.
-      Proposed by pydave at GitHub.
+      Proposed by David Briscoe.
 
 Revision 3.3.4 (2013-08-11):
 

README.rst

 
 List of the contributors in alphabetical order:
 
-- Andrea Riciputi
+- `Andrea Riciputi <https://github.com/mrrech>`_
 - Anton Butanaev
 - Caleb Adamantine
-- Elizabeth Myers
-- Jeroen Ruigrok van der Werven
-- John Eikenberry
-- Marc Weber
-- Pedro Algarvio
-- pydave at GitHub
-- Victor Salgado
-- Will Gray
-- Yuri Habrusiev
+- `David Briscoe <https://github.com/idbrii>`_
+- `Elizabeth Myers <https://github.com/Elizafox>`_
+- `Jeroen Ruigrok van der Werven <https://github.com/ashemedai>`_
+- `John Eikenberry <https://github.com/eikenb>`_
+- `Marc Weber <https://github.com/MarcWeber>`_
+- `Pedro Algarvio <https://github.com/s0undt3ch>`_
+- `Victor Salgado <https://github.com/mcsalgado>`_
+- `Will Gray <https://github.com/graywh>`_
+- `Yuri Habrusiev <https://github.com/yuriihabrusiev>`_

syntax/python.vim

 "   Andrea Riciputi
 "   Anton Butanaev
 "   Caleb Adamantine
+"   David Briscoe
 "   Elizabeth Myers
 "   Jeroen Ruigrok van der Werven
 "   John Eikenberry
 "   Marc Weber
 "   Pedro Algarvio
-"   pydave at GitHub
 "   Victor Salgado
 "   Will Gray
 "   Yuri Habrusiev