Add license file, tests and other information to distribution

We are required to distribute a copy of the license file with the code. 
Including license and tests here also makes it easier to include and use 
them in conda-forge. 

These extra files also enable users to download the source code and 
examples to an editable location without using git. Then they can finish 
installation via `pip install --editable .`

MANIFEST.in

@@ -0,0 +1,10 @@
+recursive-include tests *
+recursive-include examples *
+include README
+include LICENSE
+include AUTHORS
+include CHANGELOG.txt
+include INSTALL
+include DEV_INSTALL.txt
+include how_to_collaborate.txt
+include run_tests.py

setup.py

@@ -31,7 +31,7 @@ def read(*rnames):
     maintainer='Switch Authors',
     maintainer_email='[email protected]',
     url='http://switch-model.org',
-    license='Apache v2',
+    license='Apache License 2.0',
     platforms=["any"],
     description='Switch Power System Planning Model',
     long_description=read('README'),