Update custom env doc to match gym API (#597)

* Update to use new close API

* Update custom env documentation to reflect new gym close API

* Update changelog.rst

* Clarifies what reset returns

* Update changelog.rst

docs/guide/custom_env.rst

@@ -34,9 +34,13 @@ That is to say, your environment must implement the following methods (and inher
 
     def step(self, action):
       ...
+      return observation, reward, done, info
     def reset(self):
       ...
-    def render(self, mode='human', close=False):
+      return observation  # reward, done, info can't be included
+    def render(self, mode='human'):
+      ...
+    def close (self):
       ...
 
 

docs/misc/changelog.rst

@@ -67,6 +67,8 @@ Documentation:
 - Fix outdated source documentation for load_results
 - Add PPO_CPP project (@Antymon)
 - Add section on C++ portability of Tensorflow models (@Antymon)
+- Update custom env documentation to reflect new gym API for the `close()` method (@justinkterry)
+- Update custom env documentation to clarify what step and reset return (@justinkterry)
 
 Release 2.8.0 (2019-09-29)
 --------------------------
@@ -547,4 +549,4 @@ Thanks to @bjmuld @iambenzo @iandanforth @r7vme @brendenpetersen @huvar @abhiskk
 @EliasHasle @mrakgr @Bleyddyn @antoine-galataud @junhyeokahn @AdamGleave @keshaviyengar @tperol
 @XMaster96 @kantneel @Pastafarianist @GerardMaggiolino @PatrickWalter214 @yutingsz @sc420 @Aaahh @billtubbs
 @Miffyli @dwiel @miguelrass @qxcv @jaberkow @eavelardev @ruifeng96150 @pedrohbtp @srivatsankrishnan @evilsocket
-@MarvineGothic @jdossgollin @SyllogismRXS @rusu24edward @jbulow @Antymon @seheevic
+@MarvineGothic @jdossgollin @SyllogismRXS @rusu24edward @jbulow @Antymon @seheevic @justinkterry