loadShader(), shader() were missing on listing 4.1

https://github.com/processing/processing-web/issues/144
Add missing loadShader(), shader() instructions

My previous commit fixed the program at 4.1, but introduced a mistake in the flow of the explanation. This commit should deal with that. 

The wording can be probably improved (non native English speaker here).
Removed video lib from reference generation script
Updated ref build script; now requires processing-video repo to be nearby, alongside processing and processing-web
People page updates
People page updates
People page updates
5 radio button to donation form
Pointed issues links to wiki, for clear explanation of how to report bugs
adding additional customer data to purchase log file
Merge branch 'master' of https://github.com/processing/processing-web
cleaning up timestamp in the purchase log file
cleaner date string for purchase log file
cleaner date string for purchase log file
Merge pull request #385 from hamoid/patch-1

loadShader(), shader() were missing on listing 4.1
Updated contributions list.
Merge branch 'master' of https://github.com/processing/processing-web

# By Scott Murray (6) and others
# Via amongiants (2) and Casey Reas (1)
* 'master' of https://github.com/processing/processing-web:
  cleaner date string for purchase log file
  cleaner date string for purchase log file
  cleaning up timestamp in the purchase log file
  adding additional customer data to purchase log file
  Pointed issues links to wiki, for clear explanation of how to report bugs
  5 radio button to donation form
  People page updates
  People page updates
  People page updates
  Updated ref build script; now requires processing-video repo to be nearby, alongside processing and processing-web
  Removed video lib from reference generation script
  Add missing loadShader(), shader() instructions
  loadShader(), shader() were missing on listing 4.1