BugFix: #69 precision bug

[lxzmxl]

#69 bugfix

[JCash]

I'm sorry, but it seems you've got this the wrong way around.
The defines are there so that you can change them, without needing a PR.

See the documentation here:

#define JC_VORONOI_IMPLEMENTATION
#define JCV_REAL_TYPE double
#define JCV_ATAN2 atan2
#define JCV_SQRT sqrt
#define JCV_FLT_MAX DBL_MAX
#define JCV_PI 3.141592653589793115997963468544185161590576171875
//define JCV_EDGE_INTERSECT_THRESHOLD 1.0e-10F
#include "jc_voronoi.h"

Also, it's not good practice to change someone elses formatting.
E.g. I don't use clang format, so please use the style in the file.

And the unit tests are failing.