Drop support for Python 2

1. Remove use of six, and remove mention of its requirement in setup
2. No longer attempt to infer MKL location from numpy's distutils
   Always require MKLROOT variable to be set.

Author: oleksandr-pavlyk

setup.py

@@ -60,16 +60,12 @@
 
 
 def get_extensions():
-    try:
-        from numpy.distutils.system_info import get_info
-        mkl_info = get_info('mkl')
-    except ImportError:
-        mkl_root = os.environ['MKLROOT']
-        mkl_info = {
-            'include_dirs': [join(mkl_root, 'include')],
-            'library_dirs': [join(mkl_root, 'lib'), join(mkl_root, 'lib', 'intel64')],
-            'libraries': ['mkl_rt']
-        }
+    mkl_root = os.environ['MKLROOT']
+    mkl_info = {
+        'include_dirs': [join(mkl_root, 'include')],
+        'library_dirs': [join(mkl_root, 'lib'), join(mkl_root, 'lib', 'intel64')],
+        'libraries': ['mkl_rt']
+    }
 
     mkl_include_dirs = mkl_info.get('include_dirs', [])
     mkl_library_dirs = mkl_info.get('library_dirs', [])
@@ -99,7 +95,7 @@ def get_extensions():
             sources=['mkl/_mklinitmodule.c'],
             define_macros=defs,
             include_dirs=mkl_include_dirs,
-            libraries=mkl_libraries,
+            libraries=mkl_libraries + ["pthread"],
             library_dirs=mkl_library_dirs,
             extra_compile_args=[
                 '-DNDEBUG'
@@ -155,7 +151,7 @@ def setup_package():
         test_suite='nose.collector',
         python_requires='>=2.7,!=3.0.*,!=3.1.*,!=3.2.*,!=3.3.*',
         setup_requires=['setuptools', 'cython'],
-        install_requires=['six'],
+        install_requires=[],
         packages=setuptools.find_packages(),
         ext_modules=get_extensions()
     )