One minor editorial change at the end of chapter 1.
added code for tracking alleles over generations
Merge remote-tracking branch 'origin/master'
Removed popgen_notes.pdf from git tracking by the following command:

git rm --cached popgen_notes.pdf

Conflicts:
	popgen_notes.pdf
Merge https://github.com/saeschba/popgen-notes-gc
merging with Simon's notes