Improve the wording for computed text position alignment

The text position alignment is always set, and the auto value is not
special in the same sense as for line and position.
Merge pull request #107 from foolip/computed-special-value-auto

Improve the wording for computed text position alignment
Add separate enums for lineAlign and positionAlign

https://www.w3.org/Bugs/Public/show_bug.cgi?id=26016
Merge pull request #109 from foolip/align-enums

Add separate enums for lineAlign and positionAlign
Drop punctuation trailing "If ..." in switches

The original WebVTT spec and current HTML spec does not use this style,
and no punctuation is still more common in this file.
Merge pull request #110 from foolip/switch-if-colon

Drop punctuation trailing "If ..." in switches
Add a missing </p>
Merge pull request #112 from foolip/missing-p

Add a missing </p>
Merge commit 'd4bacf9148bbdd95753b7c3cd9fc3c4c3fbbdd6b' into revert-regions
Merge commit '2687f4f704726047c703044046548e0dfab2969e' into revert-regions

Conflicts:
	webvtt.html
Merge commit 'a862c015899872fe74fa17f4b30902a17d736b10' into revert-regions

Conflicts:
	webvtt.html