Allow disable-noqa to take a comma-separated list

A bare --disable-noqa option still sets the value to True,
this adds boolean strings, e.g. --disable-noaq=true,
as well as a comma-separated list of codes to disable noqa for.

Changes the is_inline_ignored method to accept both the boolean
and comma-separated list values and act appropriately.

Fixes #667

docs/source/manpage.rst

@@ -64,6 +64,11 @@ All options available as of Flake8 3.1.0::
                           E,F,W,C90)
     --disable-noqa        Disable the effect of "# noqa". This will report
                           errors on lines with "# noqa" at the end.
+                          May be a bare flag, a boolean value, or a
+                          comma-separated list of errors to disable "# noqa"
+                          for.
+                          A bare flag or a boolean true will disable all
+                          "# noqa"s.
     --show-source         Show the source generate each error or warning.
     --statistics          Count errors and warnings.
     --enable-extensions=ENABLE_EXTENSIONS

docs/source/user/options.rst

@@ -621,11 +621,16 @@ Options and their Descriptions
     file. This option allows you to see all the warnings, errors, etc.
     reported.
 
+    In addition to a bare flag, this option also accepts a boolean value
+    or a comma-separated list of codes to disable ``# NOQA`` for.
+
     Command-line example:
 
     .. prompt:: bash
 
         flake8 --disable-noqa dir/
+        flake8 --disable-noqa=true dir/
+        flake8 --disable-noqa=E432,E5,W dir/
 
     This **can** be specified in config files.
 
@@ -635,6 +640,10 @@ Options and their Descriptions
 
         disable_noqa = True
         disable-noqa = True
+        disable_noqa =
+            E432,
+            E5,
+            W
 
 
 .. option:: --show-source