Feat d3 improv

In this pull-request:

 1. Added tests for various calls, adopted from D3's tests.
 2. Fixed type problems with some of the setters and getters of accessors.
 3. Added some missing functions (in Nest) and fixed some incorrect ones (Arc, centroid)
 4. Made the a little more `v0.9.1` friendly (renamed `bool` to `boolean`, avoided overloading functions by return type, fixed names of types/modules)

I ran into a compiler issue with one of the tests. The issue does not happen with the `devel` version of the compiler. I have included the test in the body nevertheless.