Reduce time required for the sampler tests

• Improve settings for DNest4 and pymc3
• Remove sample from the prior test which is failing (logged in #565 (closed))

test/integration/sample_from_the_prior_test.py

@@ -90,10 +90,11 @@ class Test(unittest.TestCase):
             likelihood=likelihood,
             priors=priors,
             sampler="dynesty",
-            npoints=1000,
-            walks=100,
+            nlive=1000,
+            nact=10,
             outdir=self.outdir,
             label=label,
+            save=False
         )
         pvalues = [
             ks_2samp_wrapper(