govuk_spinup: don't assume a bash shell, rbenv...
govuk_spinup: don't assume a bash shell, rbenv...

rbenv assumes that the shell is bash, which is rather tedious. Extract the
relevant parts from "rbenv init -" and put them directly in govuk_spinup.

alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet