Issue #2976

See https://developers.google.com/closure/templates/ for documentation.
Closure Templates support text, HTML, JS and CSS code.

I'm not extremely happy with the indentation which is currently based
just on the Soy tags, not on the underlying code. Although this style
is possible and sometimes used, it's not the most common style.

Completing inside a word used to try and take the whole word into
account. This is not typical completion behavior, and often not what
you want. After this change, the addons only take the part of the
word in front of the cursor into account.

A loop is caused in the Puppet mode when adding a capital letter
due to an incomplete regex match and use of the backUp function.
Resolving this issue required checking for a full match against
the word before calling backUp on the stream.

Issue #2967

Issue #2969

Issue #2967

Remove a bunch of convoluting abstractions, make sure the regexps are
actually cached.

Issue #2964

Closes #2960

Issue #2952

Issue #2928
Issue #2958

The gfm mode is for the GitHub flavour.

The mime type is currently accounted for in the htmlembedded definition, but erb
is not listed in the `mode/meta.js` index.

- more style classes: operator, builtin, meta, brackets
- literal metas (@ and ^^)
- many more operators
- mime type and extension from spec

This prevents a stray $ from setting the whole rest of
the document to math mode.

Closes #2928

Issue #2920

The mode associated with a token is now the inner mode at
the time when the token is started. The htmlmixed and markdown/gfm
modes were fixed to return empty tokens during mode switches
when necessary to enforce this rule.

Issue #2919

Issue #2922