Re-apply all of the changes on the tool-symlinks branch

Revert "Revert "Merge pull request #360 from scraperwiki/20130816-tool-symlinks""

This reverts commit 51ec448f6d6898649674e414b073493e07c0ac45.
Don't delete http directory and don't symlink to tool/http
Merge pull request #373 from pwaller/20130816-tool-symlinks

1 DAY: Support tools through symlinks to /tools