Adding information about the Software Carpentry Foundation.

1.  Created `scf` directory to hold documents.
2.  Wrote `scf/index.html` with links to documents.
3.  Modified navigation bar to link to this (padding is off).
4.  Modified Makefile to rebuild when SCF material changes.
Peter Steinbach
Cleaning up nav bar
Merge branch 'master' into adding-scf-material
Adding committee roles and responsibilities
Fixing formatting of executive director page
Fix links at team.html
Merge pull request #714 from r-gaia-cs/fix-links

Fix links at team.html
Merge branch 'adding'
Merge branch 'adding-scf-material'