scipy and python3 fixes

@GregAshton These two small fixes make the package work again under current scipy (1.4.1) and python3.

gridcorner.py

 import numpy as np
 import matplotlib.pyplot as plt
 from matplotlib.ticker import MaxNLocator
-from scipy.misc import logsumexp
+try:
+    from scipy.special import logsumexp
+except ImportError:
+    from scipy.misc import logsumexp
 
 
 def log_mean(loga, axis):
@@ -157,7 +160,7 @@ def gridcorner(D, xyz, labels=None, projection='max_slice', max_n_ticks=4,
 
 
 def projection_2D(ax, x, y, D, xidx, yidx, projection, lines=None, **kwargs):
-    flat_idxs = range(D.ndim)
+    flat_idxs = list(range(D.ndim))
     flat_idxs.remove(xidx)
     flat_idxs.remove(yidx)
     D2D = projection(D, axis=tuple(flat_idxs), **kwargs)
@@ -171,7 +174,7 @@ def projection_2D(ax, x, y, D, xidx, yidx, projection, lines=None, **kwargs):
 
 def projection_1D(ax, x, D, xidx, projection, showDvals=True, lines=None,
                   **kwargs):
-    flat_idxs = range(D.ndim)
+    flat_idxs = list(range(D.ndim))
     flat_idxs.remove(xidx)
     D1D = projection(D, axis=tuple(flat_idxs), **kwargs)
     ax.plot(x, D1D, color='k')