Add ImplicitTriangleMesh3 and marchingCubes to Python API

[doyubkim]

This revision adds/fixes Python API for ImplicitTriangleMesh3 and marchingCubes. It also adds new Python example, apic_example03.py, to demonstrate new/fixed features.

[doyubkim]

This PR is motivated by Issue #191.

[codecov-io]

Codecov Report

Merging #218 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #218   +/-   ##
=======================================
  Coverage   88.15%   88.15%           
=======================================
  Files         547      547           
  Lines       36618    36618           
=======================================
  Hits        32279    32279           
  Misses       4339     4339

Impacted Files	Coverage Δ
include/jet/implicit_triangle_mesh3.h	100% <ø> (ø)	⬆️

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[PavelBlend]

The simulator does not correctly save OBJ. They are 0 bytes in size.

[doyubkim]

@PavelBlend that’s strange. What is your Python version? Where did you executed the script? Will try to reproduce.

[PavelBlend]

I ran apic_example03.py
Python version = 3.7.0 windows 64 bit

[doyubkim]

Interesting. Let me try it on a Windows machine.

[utilForever]

I'll try it today. I use Windows 10 Enterprise 64bit / Python 3.7.

[PavelBlend]

I checked in blender. And I saw that the meshes are written correctly.
Maybe the problem is in the example, and not in the API?

[doyubkim]

I've tested with a Windows machine and still works fine for me. Did you put the example script somewhere else? Empty obj files might be caused by empty sim since it couldn't find bunny.obj.

[PavelBlend]

I'm sorry. Bunny.obj was packed in the archive. Everything works correctly.

[doyubkim]

@utilForever, let me know if this PR looks fine to you.

[utilForever]

LGTM. Thank you for your work.

[utilForever]

I'm sorry. I was very busy due to year-end party and parent's house visit.

[doyubkim]

No worries. Happy holidays!