Update development release version to 0.10.0.dev0 (#2443)

In order for downstream packages to make use of the latest
pre-release features, we can pre-release versions of our packages.
For packages ending in `devN` pip will not install that package
version by default.  This change manually updates our package version
to a development version with the idea that we can manually perform
development versions with the potential for future automated / nightly
dev releases.

gym-unity/setup.py

 
 setup(
     name="gym_unity",
-    version="0.4.4",
+    version="0.4.5.dev0",
     description="Unity Machine Learning Agents Gym Interface",
     license="Apache License 2.0",
     author="Unity Technologies",
-    install_requires=["gym", "mlagents_envs==0.9.1"],
+    install_requires=["gym", "mlagents_envs==0.10.0.dev0"],
 )

ml-agents-envs/setup.py

 
 setup(
     name="mlagents_envs",
-    version="0.9.1",
+    version="0.10.0.dev0",
     description="Unity Machine Learning Agents Interface",
     url="https://github.com/Unity-Technologies/ml-agents",
     author="Unity Technologies",

ml-agents/setup.py

 
 setup(
     name="mlagents",
-    version="0.9.1",
+    version="0.10.0.dev0",
     description="Unity Machine Learning Agents",
     long_description=long_description,
     long_description_content_type="text/markdown",
     ),
     zip_safe=False,
     install_requires=[
-        "mlagents_envs==0.9.1",
+        "mlagents_envs==0.10.0.dev0",
         "tensorflow>=1.7,<1.8",
         "Pillow>=4.2.1",
         "matplotlib",