iGrad

Update me to describe iGrad

Notes

When moving from Mercurial to Git, there were two branches:

1. master held changes made a while back by John Gibson. Because performance was unacceptable, this version was not in use in production.

2. old-igrad was a branch from before the changes made by John. Ken had been using this branch in prodution for some while.

Ken had Tom rename these branches to better reflect reality.

Old Branch	New Branch
master	develop
old-igrad	master