Improve linking of twitter posts.

Closes: #148
Closes: #150
Co-written-by: C. Scott Ananian <cscott@cscott.net>
Change-Id: I9b7fb5af11aac20a00046a23f70c6b50e78f2c53
One more attempt at rationalizing chat message scroll-to-bottom.

Closes: #164
Change-Id: If5bd18423c4f2f52dcb597baceb22018186f1c7b
Use Gruber's "Liberal, Accurate Regex" for URLs when linkifying.

This ensures that we don't grab trailing punctuation in the URL
accidentally, and linkifies paths given without the leading protocol,
etc.

Change-Id: Id9a0473606b7d6301980d206fe6595d08bd34575
Fix tab completion by moving whos_here() out of helpers

deb7f72cb6 ("Use Template#helpers method to define helpers.") moved
some methods away from being on the Template object to being Spacebars
helpers.  But Template.messages_input.events was making a call to
Template.chat_header.whos_here() directly, and that doesn't work
after the refactor.

Closes: #154
Change-Id: Icfd2f0d487fb72a563b6e9004e1349a0d6d28eb0
Add Meteor platform metadata.

This was added in Meteor 0.9.4ish.

Change-Id: I2ed0858191059fe0ccea282adb985e07327fc118