Port FlatBuffers to Python.

Implement code generation and self-contained runtime library for Python.

The test suite verifies:
  - Correctness of generated Python code by comparing output to that of
    the other language ports.
  - The exact bytes in the Builder buffer during many scenarios.
  - Vtable deduplication correctness.
  - Edge cases for table construction, via a fuzzer derived from the Go
    implementation.
  - All code is simultaneously valid in Python 2.6, 2.7, and 3.4.

The test suite includes benchmarks for:
  - Building 'gold' data.
  - Parsing 'gold' data.
  - Deduplicating vtables.

All tests pass on this author's system for the following Python
implementations:
  - CPython 2.6.7
  - CPython 2.7.8
  - CPython 3.4.2
  - PyPy 2.5.0 (CPython 2.7.8 compatible)

tests/MyGame/Example/Test.py

@@ -0,0 +1,24 @@
+# automatically generated, do not modify
+
+# namespace: Example
+
+import flatbuffers
+
+class Test(object):
+    __slots__ = ['_tab']
+
+    # Test
+    def Init(self, buf, pos):
+        self._tab = flatbuffers.table.Table(buf, pos)
+
+    # Test
+    def A(self): return self._tab.Get(flatbuffers.number_types.Int16Flags, self._tab.Pos + flatbuffers.number_types.UOffsetTFlags.py_type(0))
+    # Test
+    def B(self): return self._tab.Get(flatbuffers.number_types.Int8Flags, self._tab.Pos + flatbuffers.number_types.UOffsetTFlags.py_type(2))
+
+def CreateTest(builder, a, b):
+    builder.Prep(2, 4)
+    builder.Pad(1)
+    builder.PrependInt8(b)
+    builder.PrependInt16(a)
+    return builder.Offset()