Expand the searching for the "free_operators" function.  As a nested
class' parent is a class, we need to "recurse" up to find the namespace
declaration which contains the list of free_operators.

Expand the nested classes test to contain an operator and a friend
operator.

Add support for wrapping a class which has a nested class within it.

* Add checking for "classes" key in wrapping data
* Switch to "returning" modules for all function calls
* Pass those modules into the init functions when possible.
* Add nested class tests
* Fix nested classes in inheritance_features test

Major functionality to go:
  * Template classes with nested classes will currently only nest in the
last instance added.  Switch to init functions for each version so that
we can properly add nested classes to each.

Add Eigen to CI

See merge request autopybind11/autopybind11!120

Account for friend decorator in operators.

Closes #130

See merge request autopybind11/autopybind11!106

Prevent extraneous namespace file generation

Closes #154

See merge request autopybind11/autopybind11!122

First, find operators that do not have the same parent
as the target function.  Then when writing the operators, use a special
formatting (lambda) to properly add the friend operator.

See https://github.com/josephsnyder/drake-external-examples/issues/3
for additional information.

Process "operator<<" as "__str__"

Represent the operator<< object as the function that returns the string
representation of the object, if the first argument is "std::ostream".

Use a stringstream and return the representation to be printed.  This
seems to account for friend operator<< objects.

Account for istream objects.

Additional fixes to stream operator handling

1. Account for both ostream and istream objects.
  1.a Only wrap the ostream objects for now.
2. Selectively add sstream as an include when a stream object is found.

Additional formatting fixes.

Add keep_alive customization

See merge request autopybind11/autopybind11!113

Add a default keep_alive flag to the customization data. Adds a
"py::keep_alive<1, 2>",

TODO: allow specification of keep_alive parameters?

Converge to skiplist for functions to ignore.

See merge request autopybind11/autopybind11!118

Dev/rework flag names

Closes #149

See merge request autopybind11/autopybind11!115

Converge terminology for list of objects to not wrap to use skiplist
instead of blacklist.

Add component filters

See merge request autopybind11/autopybind11!110

# Conflicts:
#   autopybind11/__main__.py

Fix tramp copy constructor

See merge request autopybind11/autopybind11!114

README: Add reference to FFIG

See merge request autopybind11/autopybind11!116

Support long type template instantiations

Differ checks between class level and member/functions