use np.close to check to check for vanishing denom

Just to offer users some amount of control over the tolerance.

svgpathtools/path.py

@@ -572,7 +572,7 @@ class Line(object):
             d = (other_seg.start.imag, other_seg.end.imag)
             denom = ((a[1] - a[0])*(d[0] - d[1]) -
                      (b[1] - b[0])*(c[0] - c[1]))
-            if abs(denom) < 1e-9:
+            if np.isclose(denom, 0):
                 return []
             t1 = (c[0]*(b[0] - d[1]) -
                   c[1]*(b[0] - d[0]) -