Prevent users to set state when the form is unmounted (#895)
Prevent users to set state when the form is unmounted (#895)

* Prevent setFieldValue to go through when unmounted

setFieldValue sets state, and nothing prevents users of this library to call it when unmounted

* Prevent setSubmitting to go through if unmounted

jaredpalmer/formik,jaredpalmer/formik,jaredpalmer/formik