Update formal.tex

Changed the period ending the line to a colon, to be consistent with lines 285 and 294, and to avoid a lowercase letter following a period.
Merge pull request #745 from Pierre-Yves-Gaillard/patch-1

Update formal.tex
changed "resultion" to "resolution" on line 3
Merge pull request #747 from Pierre-Yves-Gaillard/patch-1

changed "resultion" to "resolution" on line 3
Last rule of Section A.2.2, lines 591 and 592

In the last rule of Section A.2.2 I put

* A : \UU_i instead of A \equiv A' : \UU_i in the first hypothesis, and 

* B : \UU_i instead of B \equiv B' : \UU_i in the second hypothesis.

(See lines 591 and 592 of 

https://github.com/HoTT/book/blob/master/formal.tex#L591 )

I think this corrects a typo, but I am far from being sure I am right.
Merge pull request #748 from Pierre-Yves-Gaillard/patch-2

Last rule of Section A.2.2, lines 591 and 592
Merge remote-tracking branch 'origin/master' into patch-1