changes to the Hindley-Milner Inference chapter

[chsievers]

Small and not so small changes to the beginning of chapter 7.

[sdiehl]

Sweet, I'll look over the changes this weekend. Have you tried rendering the latex either using pdflatex or mathjax.

Sometimes line like this:

we get
$$[s]\alpha=\alpha\rightarrow\beta$$
and

Need an extra space between the display equations to render in the browser.

we get

$$[s]\alpha=\alpha\rightarrow\beta$$

and

[chsievers]

At least the mathjax version renders fine for me.