Update examples to work with latest version

This includes sub-optimal repitition of transition event handlers: we must
bind the same handler to both the `enter:transition` event *and* the
`update:transition` event. Ideally, we would bind it once to the
`merge:transition` event, but making this selection cancels
previously-scheduled transitions on the `enter` and `update` selections...

This also highlights a problem with the current mixin API: handlers for
lifecycle events in "mixin" charts cannot access the chart into which they
have been mixed. In other words, layers in these mix in charts can only
access the chart they have been defined within...
adding  options argument that can take a  property pointing to another chart, specifically for the usecase in which one mixes in a chart but wishes the parent chart to be the context chart within a lifecycle callback.
When calling .off on a layer, check the callback of the handler (now that we store { callback, chart } objects rather than just callbacks.
Fix bug in `Layer#off` and add test coverage

Correct naive error in list manipulation. Increase test coverage to
include the previously-untested `Layer#off`.
Move tests for Layer's `chart` context

Because this functionality is implemented entirely within `d3.layer`,
the associated tests do not need to excersize functionality from
`d3.chart`.
Remove unused variables
Merge pull request #11 from misoproject/mixin.chart.context

Resolves #10 - Navigating mixins from lifecycle event handlers
Rename Layer's `base` property

The Layer's `base` attribute is not accessible to consumers of the
d3.chart API. In order to better communicate this detail (and make the
source code more readable), prefix the attribute name with an underscore.

Resolves #14.
Normalize `mixin` API

Mixin declarations should be similar to te Layer and Chart APIs. Namely,
the first argument to `Chart#mixin` should be the Chart name, the second
should be the selection for the mixin's base, and all following
arguments should be passed through to the mixin Chart's constructor.
Fix bug in example Chord diagram

This chart was not built to be re-drawn, so a slight modification is
necessary to enable multiple calls to `Chart#draw`.
Merge pull request #17 from misoproject/mixin-args

Normalize `mixin` API
Merge pull request #18 from misoproject/hybrid-leak

Fix bug in example Chord diagram
Remove debugging statement from tests
Permit global `teardown` function in tests
Update project authors

Name authors according to conventions recommended by NPM:
https://npmjs.org/doc/json.html
Release v0.1.0
adding some links to the readme for folks to get started
Merge pull request #20 from misoproject/readme.update

Adding some links to the readme for folks to get started
Update license