Cache Object.hasOwnProperty

Using an alias is slightly more efficient and slightly more readable.
Fix minor code style inconsistencies
Rename files

For source and test files, 'd3' is implied, so namespacing is unecessary.
Fix error in readme
Correct mixin iteration logic

Since the internal `_mixins` object is an Array, it should not be
iterated with for..in.
Remove unused build tasks
Re-factor d3.layer unit tests to be more focused
Fix typo
Add unit test for lifecycle event invocation order

Resolves GitHub issue #15
Throw error when instantiating unrecognized charts

This explicit error is more instructive than what is currently being
thrown in this case:

    Uncaught TypeError: Cannot read property 'prototype' of undefined