Add solutions to the union exercises.
Minor cosmetic edits, nothing much noteworthy.

I did comment out some of @wei2912's work, because I plan on redoing/editing it
later.
Merge pull request #68 from pharpend/f-union-exercises

Add friendlier solutions to the union exercises, some cosmetic edits
Merge branch 'develop' into f-chapterstar

Conflicts:
	book/lysa.ltx