chap1 - motiviation etc

[lachlandeer]

New structure:

1. What is Snakemake & why we use it

2. Working Example
   two lines on the paper does
   copy one table from paper and fig and say we want to reproduce paper (i..e repro paper results)

3. way forward
   part 1 does this ... part 2 does that etc

we can pull some of the preface content in here coz the first bit is probably too long

Note - we may want to talk about importance reproducibility later on