Fixes #428. This is built on top of existing tick support for linear scales: for
small intervals, a linear scale computes ticks based on milliseconds; for large
intervals, a linear scale computes ticks based on fractional years. This commit
also extends the time scale's formatter to display milliseconds.

The second argument, n, is optional.

Fixes #471. This prevents transition.remove() from clobbering another transition
"end" event listener, or vice versa.

See #136.

Fixes #446.

There's an edge condition which is not discussed in the original algorithm
("Visualization of Large Hierarchical Data by Circle Packing", Wang et. al):
what happens if the first intersecting circle C_j is equidistant from C_m and
C_n? In other words, it is both after C_n on the front-chain, and before C_m.
The correct answer is that you should splice the smaller of the two circles. If
C_m is smaller than C_n, then splice from C_j to C_n and set C_m to C_j;
otherwise, splice from C_m to C_j, and set C_n to C_j.

Simplification to spline example.

The tick sizes need to be set, else they grow from zero.

A small optimisation: only call insertBefore() if node.nextSibling isn't
already what we want, so that document nodes that are already in the
correct order can be skipped.

Fixes #395.

Fixes #412.

Also, set vows version to "0.6.x" as the exact patch version is not
important right now.

corrected fix for the calendar example: do NOT mix UTC and Local TimeZone date operations in calculations which depend on identifying day/month transitions - default JavaScript Date object works with 'local timezone'. Fix tested in AZ/USA and Amsterdam/EUR timezones.