Added blank section "how to read this book"

This is something most books have, and will be important later on.
Merge branch 'f-pedantry' into develop
Merge branch 'develop' of github.com:learnmath/lysa into develop
Refactor required software notes.

* Add per-OS install instructions for Gentoo and Ubuntu.
* Move the Magit thing to be a sub-point of the Emacs thing.
Fix ambiguous note about learning Haskell.

It no longer implies that learning Haskell is required, instead gives
resources/suggestions if the contributor doesn't know Haskell.
Add note about git add -p.
Split the contrib guide up into sections.
Add note about erlang git commit guide.
Note about adding to the \author field and #40.
Merge branch 'f-contribfixes' into develop
Merge pull request #39 from pharpend/develop

adjusted contrib and added new content