Warning in Analysis Tutorial

[bkushigian]

Doing the Analysis tutorial I get the following warning:

> (let zero (bigrat (bigint 0) (bigint 1)))
[WARN ] In 1:1-41: (let zero (bigrat (bigint 0) (bigint 1)))
    Global `zero` should start with `$`. Enable `--strict-mode` to turn this warning into an error. Suppressing additional warnings of this type.

[saulshanabrook]

We made this change after this was created. We should update the global variables to all be prefixed by $