Minor typo correction
Fix typo
Minor change to phrasing
Fix spelling typo
Merge pull request #149 from williamscott/master

Minor editing changes on Chapter 2
Delete blank line in code
Made reference link live
Chapter 3 typo correction

1.  replace "that is does" with "that this does"
2.  add "a" to "using loss function"
3. replace "parameter of interested" with "parameter of interest"
Correct typos

1. "scraping" replaces "scrapping"
2. Correct spelling of equivalence
3. Add hyperlink for Reference 2
Merge pull request #151 from williamscott/master

Minor editing changes to chapters 2 and 3
Merge pull request #1 from CamDavidsonPilon/master

latest from upstream