fix #180: couldn't type >1 spaces in RootTextBlock
'.end' => '.ends'

sed -i '' 's/\.end[[:>:]]/.ends/g' src/*.js

EXCEPT don't replace .end on Bracket's

Except for `.end` and `.endChild`, our convention has pretty
consistently been that collections are pluralized (e.g.  `LatexCmds`);
`.endChildren` is just such a mouthful though, so we're going with
`.ends` for both. They never conflict, `Fragment`s were the ones with
`first` and `last` and `Node`s were the ones with `{first,last}Child`,
and `node.ends[L]` can make sense as `node`'s leftmost child.

https://github.com/mathquill/mathquill/pull/160#issuecomment-16459573
'endChild' => 'ends'

sed -i '' 's/[[:<:]]endChild[[:>:]]/ends/g' src/*.js test/unit/*.js

Except for `.end` and `.endChild`, our convention has pretty
consistently been that collections are pluralized (e.g.  `LatexCmds`);
`.endChildren` is just such a mouthful though, so we're going with
`.ends` for both. They never conflict, `Fragment`s were the ones with
`first` and `last` and `Node`s were the ones with `{first,last}Child`,
and `node.ends[L]` can make sense as `node`'s leftmost child.

https://github.com/mathquill/mathquill/pull/160#issuecomment-16459573
use ` to mark variables in comment #cosmetic #comment
fix #190 $ at end of TextBlock causes errors later

2a4189c7be7162622d9c9b3b252c9c3f5d5b843f should've done this:
https://github.com/mathquill/mathquill/commit/2a4189c7be7162622d9c9b3b252c9c3f5d5b843f#L0R492
fix #152 renderLatex errors if selected to edge

after mutating this.ends, writeLatex disowns the selection, but the ends
of the selection are now malformed