add autoflake fixer (#3779)

* first attempt

* added autoflake executable

* added Windows executable for appveyor

* delete unused files

* corrected wrong sorting

doc/ale-python.txt

@@ -43,6 +43,33 @@ ALE will look for configuration files with the following filenames. >
 The first directory containing any of the files named above will be used.
 
 
+===============================================================================
+autoflake                                                *ale-python-autoflake*
+
+g:ale_python_autoflake_executable           *g:ale_python_autoflake_executable*
+                                            *b:ale_python_autoflake_executable*
+  Type: |String|
+  Default: `'autoflake'`
+
+  See |ale-integrations-local-executables|
+
+
+g:ale_python_autoflake_options                 *g:ale_python_autoflake_options*
+                                               *b:ale_python_autoflake_options*
+  Type: |String|
+  Default: `''`
+
+  This variable can be set to pass extra options to autoflake.
+
+
+g:ale_python_autoflake_use_global           *g:ale_python_autoflake_use_global*
+                                            *b:ale_python_autoflake_use_global*
+  Type: |Number|
+  Default: `get(g:, 'ale_use_global_executables', 0)`
+
+  See |ale-integrations-local-executables|
+
+
 ===============================================================================
 autoimport                                              *ale-python-autoimport*
 
@@ -69,6 +96,7 @@ g:ale_python_autoimport_use_global             *g:ale_python_autoimport_use_glob
 
   See |ale-integrations-local-executables|
 
+
 ===============================================================================
 autopep8                                                  *ale-python-autopep8*
 

doc/ale-supported-languages-and-tools.txt

@@ -399,6 +399,7 @@ Notes:
   * `purescript-language-server`
   * `purty`
 * Python
+  * `autoflake`!!
   * `autoimport`
   * `autopep8`
   * `bandit`

doc/ale.txt

@@ -2933,6 +2933,7 @@ documented in additional help files.
   pyrex (cython)..........................|ale-pyrex-options|
     cython................................|ale-pyrex-cython|
   python..................................|ale-python-options|
+    autoflake.............................|ale-python-autoflake|
     autoimport............................|ale-python-autoimport|
     autopep8..............................|ale-python-autopep8|
     bandit................................|ale-python-bandit|