Generalized zentangle bracelet

This is generalized version of [Zentangle bracelet](https://www.thingiverse.com/thing:1562673). You may customize the zentangle on the bracelet. Take a look at the description of [Symmetrical triangle generator](https://www.thingiverse.com/thing:1213278) if you want to know how to design you own bracelet.

For examples, the following parameters:

- radius = 25
- height = 30
- xs = "10 -6.5 -3 0"
- ys = "-6 -6 0 0"
- triangle_side_length = 20
- line_width = 1.25
- thickness = 2
- fn = 24

will generate a model like this:


And the following parameters:

- radius = 25
- height = 30
- xs = "0 1.5 1.5 -4 -6.5"
- ys = "0 2.5 -6 -6 0"
- triangle_side_length = 20
- line_width = 1.25
- thickness = 2
- fn = 24

Generate it:

![zentangle bracelet 2](http://thingiverse-production-new.s3.amazonaws.com/renders/eb/93/4f