Improve the compatibility of the length filter with that of PHP Twig

 This follows from the discussion at schmittjoh/twig.js#53
 https://github.com/schmittjoh/twig.js/issues/53

 In short, the length filter shouldn't throw an error if the value being
 filtered isn't countable.
Failing test for schmittjoh/twig.js#45

Bug confirmed.
Fix a small typo in the failing test for schmittjoh/twig.js#45. Oops!
Fixes schmittjoh/twig.js#45 by escaping all . characters with backslashes

This is pain relief for the symptoms reported in the issue, but it doesn't cure
the underlying problem, which is that Javascript's string manipulation is
actually kind of sucky.

The ideal fix for this issue would have been to use Mozilla's non-standard third
String.replace parameter and replace the line with the following:

    str = str.replace(key, map[key], 'g');

This trivially fixes the whole problem, but it's useless because it only works
on Firefox.

Alternatively, it'd be nice if Javascript provided a native way of escaping
strings for use in regular expressions, like PHP's preg_quote
(http://php.net/preg_quote).

Since neither of these things are part of this reality, we are stuck with an
awkward problem. Perhaps a future version of twig.js ought to perform this
escaping for all such characters: . \ + * ? [ ^ ] $ ( ) { } = ! < > | : -

In the meantime, this is a nice safe, small commit, and it fixes the issue.
Recompiliation for schmittjoh/twig.js#45
Introduce a Makefile to reduce configuration and setup, and streamline building

I now understand why this project uses Closure Compiler. However, I think the
recompilation step is a little clumsy and this is preventing people from
contributing to the project as effectively as they could be.

This commit removes the need for developers to go hunting for a copy of
plovr.jar and then configure $_SERVER['PLOVR_BIN'] in ./config.php. The Makefile
knows where to get plovr, installs it to a known location, and invokes it in
that location when building the assets.

It'll only attempt to fetch plovr if it's not already present at bin/plovr.
Anybody with edge-case needs who wants a specific version of plovr.jar can cope
by placing their version in bin/plovr, without impacting those who simply want
to get on with building the assets.
Change vendor name in composer.json so I can publish an alternate version
Merge branch 'easier-building'
Merge branch 'replace-dot'

Conflicts:
	twig.js
Merge branch 'length-compatibility'
Rebuild assets for length-compatibility