Update novice r lesson 01 to drop seq

Per a conversation with @jdblischak I have removed the section in the first lesson that used seq() to index a data.frame.

This was originally included to mirror the first python lesson which used strides (see #692) That has been removed and this simply keeps that first novice R lesson in-line with that change.

Both the .Rmd and .md files have been updated.

p.s. second attempt as I am learning new things about github!