requirements-dev: Update setup.py to support sdist build with scikit-build>=0.5.0

This is needed because following scikit-build/scikit-build@a371ed2, scikit-build
whilelists commands expecting CMake to be run.

See http://scikit-build.readthedocs.io/en/latest/usage.html#setup-options

Author: jcfr

requirements-dev.txt

@@ -6,5 +6,5 @@ pytest>=3.0.3
 pytest-cov>=2.4.0
 pytest-runner>=2.9
 pytest-virtualenv>=1.2.5
-scikit-build>=0.4.0
+scikit-build>=0.5.0
 virtualenv>=15.0.3

setup.py

@@ -39,6 +39,7 @@ def _parse_requirements(filename):
     packages=['ninja'],
 
     cmake_install_dir='ninja/data',
+    cmake_with_sdist=True,
 
     entry_points={
         'console_scripts': [