fix some too-long lines in ustrade format
explain ctx judgment more, fix #315
errata
Merge pull request #327 from mikeshulman/ctx

explain ctx judgment more, fix #315
Merge pull request #328 from mikeshulman/errata

Make a list of errata
Merge pull request #326 from mikeshulman/formatting

fix some too-long lines in ustrade format
Fix file permissions

The files .gitignore and torus-clipped.xcf were
executable by accident.
Merge pull request #329 from vog/fix-permissions

Fix file permissions
slightly better fixes to close #330
There is a line in which a reference is inside a maths environment
(enforced by `\ensuremath`).  As these are references, they are
actually text elements so should be in `\text` commands.
Merge pull request #332 from loopspace/upstream

Put references that are in maths mode in a `\text` command
Fix definition of pair^=
Merge pull request #334 from rpglover64/master

Fix definition of \pairpath in section 2.6
Fix type typo in the proof of theorem 2.6.4
Merge pull request #337 from rpglover64/master

Typo in the proof of theorem 2.6.4