Updated links for Box2D and Mother libraries.
Merge branch 'master' of https://github.com/processing/processing-web

# By Filip Visnjic (2) and REAS (2)
# Via REAS
* 'master' of https://github.com/processing/processing-web:
  Modified credit for Phantogram exhibition
  link edit
  March exhibition update
  New Processing logo at 256 x 256 pixels