added first pass at pages on community, contributing apps
Merge pull request #79 from rjleveque/community

added first pass at pages on community, contributing apps
Add link to HPC^3 2011.
fixed superscript in HPC3, reformatted
Merge pull request #80 from ketch/hpc3_2011_link

Add link to HPC^3 2011.
Add variable bc additions to list.
cleaned up list of HPC3 workshops
add link to geoclaw.org and remove old comment
Added note that design-a-grid has disappeared
Merge pull request #81 from rjleveque/ngdc

design-a-grid comments and cleaned up HPC3 list