Stop using deprecated pkg_resources

Use NumPy’s own `np.lib.NumpyVersion` to test NumPy versions.

Fixes #67

Author: musicinmybrain

src/pyemd/emd.pyx

@@ -3,8 +3,6 @@
 # distutils: language = c++
 # emd.pyx
 
-from pkg_resources import parse_version
-
 from libcpp.pair cimport pair
 from libcpp.vector cimport vector
 import cython
@@ -142,7 +140,7 @@ def euclidean_pairwise_distance_matrix(x):
 
 
 # Use `np.histogram_bin_edges` if available (since NumPy version 1.15.0)
-if parse_version(np.__version__) >= parse_version('1.15.0'):
+if np.lib.NumpyVersion(np.__version__) >= np.lib.NumpyVersion('1.15.0'):
     get_bins = np.histogram_bin_edges
 else:
     def get_bins(a, bins=10, **kwargs):