Punctuation set is different from the spec

[rlidwka]

CommonMark/spec.txt defines this punctuation set:

!"#$%&'()*+,-./:;<=>?@[\]^_`{|}~

Regexp in commonmark.js/lib/inlines.js uses smaller character set:

!"#%&'()*,-./:;?@[\]_{}

As a result, ^_test_ is not rendered as emphasis, even though according to spec it should (and cmark renders it as an emphasis).

$ echo '^_test_' | ./cmark/build/src/cmark 
<p>^<em>test</em></p>
$ echo '^_test_' | ./commonmark.js/bin/commonmark 
<p>^_test_</p>

Original issue: markdown-it/markdown-it#380

[SamSaffron]

Note, fixing this will cause:

https://derp.com?_test_=1

To render as:

<p>https://derp.com?<em>test</em>=1</p>

It is 100% correct to fix the implementation so it correctly implements the spec, but the spec does do some weird things with legit URLs in the wild.