Add --bug-report flag to help bug reporters

When invoked it will print out JSON that has all of the debugging
information needed by the maintainers to diagnose or reproduce a bug.

Closes #207

docs/source/release-notes/3.1.0.rst

@@ -0,0 +1,4 @@
+3.1.0 -- 2016-yy-xx
+-------------------
+
+- Add ``--bug-report`` flag to make issue reporters' lives easier.

docs/source/release-notes/index.rst

@@ -6,6 +6,7 @@ All of the release notes that have been recorded for Flake8 are organized here
 with the newest releases first.
 
 .. toctree::
+    3.1.0
     3.0.4
     3.0.3
     3.0.2

docs/source/user/options.rst

@@ -728,3 +728,51 @@
         flake8 --benchmark dir/
 
     This **can not** be specified in config files.
+
+
+.. option:: --bug-report
+
+    Generate information necessary to file a complete bug report for Flake8.
+    This will pretty-print a JSON blob that should be copied and pasted into a
+    bug report for Flake8.
+
+    Command-line usage:
+
+    .. prompt:: bash
+
+        flake8 --bug-report
+
+    The output should look vaguely like:
+
+    .. code-block:: js
+
+        {
+          "dependencies": [
+            {
+              "dependency": "setuptools",
+              "version": "25.1.1"
+            }
+          ],
+          "platform": {
+            "python_implementation": "CPython",
+            "python_version": "2.7.12",
+            "system": "Darwin"
+          },
+          "plugins": [
+            {
+              "plugin": "mccabe",
+              "version": "0.5.1"
+            },
+            {
+              "plugin": "pycodestyle",
+              "version": "2.0.0"
+            },
+            {
+              "plugin": "pyflakes",
+              "version": "1.2.3"
+            }
+          ],
+          "version": "3.1.0.dev0"
+        }
+
+    This **can not** be specified in config files.