DEV: Adds type hinting stub for zipline.api

as well as tooling and docs to generate this for each release

Also moved Cython files to package_data, so that we install them,
instead of just packaging them.

etc/gen_type_stubs.py

@@ -0,0 +1,42 @@
+import inspect
+from operator import attrgetter
+from textwrap import dedent
+
+from zipline import api, TradingAlgorithm
+
+
+def main():
+    with open(api.__file__.rstrip('c') + 'i', 'w') as stub:
+        # Imports so that Asset et al can be resolved.
+        # "from MOD import *" will re-export the imports from the stub, so
+        # explicitly importing.
+        stub.write(dedent("""\
+        from zipline.assets import Asset, Equity, Future
+        from zipline.assets.futures import FutureChain
+        from zipline.finance.cancel_policy import CancelPolicy
+        from zipline.pipeline import Pipeline
+        from zipline.protocol import Order
+        from zipline.utils.events import EventRule
+
+
+        """))
+
+        # Sort to generate consistent stub file:
+        for api_func in sorted(TradingAlgorithm.all_api_methods(),
+                               key=attrgetter('__name__')):
+            sig = inspect._signature_bound_method(inspect.signature(api_func))
+
+            indent = ' ' * 4
+            stub.write(dedent('''\
+                def {func_name}{func_sig}:
+                    """'''.format(func_name=api_func.__name__,
+                                  func_sig=sig)))
+            stub.write(dedent('{indent}{func_doc}'.format(
+                func_doc=api_func.__doc__ or '\n',  # handle None docstring
+                indent=indent,
+            )))
+            stub.write('{indent}"""\n\n'.format(indent=indent))
+
+
+if __name__ == '__main__':
+    main()