Simplification to spline example.

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.

the use of getUTCxxx() instead of getXxx() draw the wrong path for some timezone, the t1 will be previous year instead since t0 is not UTC timezoned

bugfix for D3.JS bug in calendar demo: edge around months was drawn incorrectly; this was apparent at each December month.

Array.reverse does not create a copy of the array, so we must slice first.

Thanks to "code golfer" @mbostock. :)

Fixes #405.

Fixes #406.

If there is only one node, it will be positioned at y = 0, which is
consistent with d3.layout.tree.

Fixes #396.

Using "devDependencies" prevents "vows" etc. from being installed if D3
is being installed as a dependency. I'm not sure whether "jsdom" counts
as a true dependency or not as we only really use it for the tests.

I've also added a "scripts": {"test": …} parameter, which specifies what
happens when you run "npm test".

Fixes #397.

It's like selection.sort, except it assumes that the data is already sorted;
the elements are reordered to match the selection.