(PE-3657) Updated reloaded example in README.md around `alter-var-root`
(PE-3657) Updated reloaded example in README.md around `alter-var-root`

This commit splits the `alter-var-root` and `check-for-errors!` calls
from `init` and `start` in the README.md's reloaded repl example into
independent forms rather than having them be chained together.

puppetlabs/trapperkeeper,rbramwell/trapperkeeper,camlow325/trapperkeeper,scotje/trapperkeeper,senior/trapperkeeper,senior/trapperkeeper