Update description and wiki location

README.md

-# BOINC github mirror
-See official page on how to contribute: http://boinc.berkeley.edu/trac/wiki
+# BOINC Repository
+See official page on how to contribute: https://github.com/BOINC/boinc-dev-doc/wiki/SoftwareDevelopment
 
 ## Current build status
 master: [![Build Status](https://travis-ci.org/BOINC/boinc.svg?branch=master)](https://travis-ci.org/BOINC/boinc)