cu2qu_test: don't use 'random' to gen test curves for py23 compat, load from json file

`random.randint`, which is used in `cu2qu.benchmark.generate_curve` function, yields
different results when run in Python 2.7 or 3, despite using the same `random.seed(1)`.

For this reason, the `test_results_unchanged` and `test_results_unchanged_multiple` tests
in `cu2qu_test` module fail when run under Python 2.

Backward compatibility was broken with Python 3.2 `random` module, as a side effect of
fixing a non-uniformity bug. For mor info see:

https://groups.google.com/forum/#!topic/comp.lang.python/KwALjKjF6Y4
http://bugs.python.org/issue9025

To work around this, I dumped the result of generate_curve (running from Python 3.5.2 on
OSX) to a json file, and use that to run the tests.

I also stripped the white space to reduce the file size.

```python
import random
import json
from cu2qu.benchmark import generate_curve

random.seed(1)
curves = [generate_curve() for i in range(1000)]

with open("Lib/cu2qu/test/data/curves.json", "w") as fp:
    fp.write(json.dumps(curves).replace(" ", ""))
```

fixup

Lib/cu2qu/test/cu2qu_test.py

@@ -18,10 +18,12 @@ from __future__ import print_function, division, absolute_import
 import collections
 import math
 import unittest
-import random
+import os
+import json
 
 from cu2qu import curve_to_quadratic, curves_to_quadratic
-from cu2qu.benchmark import generate_curve
+from cu2qu.test import DATADIR
+
 
 MAX_ERR = 5
 
@@ -31,9 +33,8 @@ class CurveToQuadraticTest(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
         """Do the curve conversion ahead of time, and run tests on results."""
-
-        random.seed(1)
-        curves = [generate_curve() for i in range(1000)]
+        with open(os.path.join(DATADIR, "curves.json"), "r") as fp:
+            curves = json.load(fp)
 
         cls.single_splines = [
             curve_to_quadratic(c, MAX_ERR) for c in curves]