Merge branch 'minimongo-array-updates' into devel

Actually implement updating field 'x.$.y'! Also some related cleanups.
Confirm that we hit the right URL when revoking tokens.

Require token revoke endpoints to return JSON with a `tokenRevoked` key,
to avoid being fooled by endpoints that don't understand token
revocation but just happened to return 200 status codes.
Print human-friendly error messages for common login failures.
Upgrade websocket-driver to 0.3.2

This lowers the max websocket frame length from 1GB to 64MB.

Note that due to #1648, this may not immediately affect existing
checkouts of meteor (but will get into all release builds).
further internal docs and cleanup
runner refactor - WIP
runner refactor - WIP (break runner.js up into several files)
runner refactor - WIP
runner refactor - WIP (rejigger runOnce/entry point)
getting into pretty good shape now!
minor edits
Finish documenting htmljs package
Fix typo (spotted by cscott)
Route Spacebars errors properly

Now Spacebars syntax errors (as well as html_scanner errors) go through proper error reporting channels rather than throwing exceptions.  For simple cases, we are back to showing nice errors like Handlebars did on devel, with context.

Next:  Comb the spacebars compiler for errors that are thrown or lack good line numbers.  Go through our own list of bad error messages.
tweaks
fix more Spacebars errors
Add missing 'random' dependency to retry
Merge remote-tracking branch 'origin/devel' into sso
Improve error message for <input></input>

...and other cases where we see an unexpected HTML end tag.  We'd previously say "Expected EOF", among other things.
Fix ellipsis in error display; test errors
observe-sequence: simplify and optimize by not fetching cursors that change