mention that pexpect ships in IPython.external

and only check for it on posix
only put Python major version in wheel tags

results in 'py2-none-any' instead of 'py27-none-any'.

This is supported by pip and PEP 425, but not available from bdist_wheel by default.
exclude notebook checkpoints from manifest
platform-dependent requirements

in bdist_wheel
always construct requirements
whitelist installed components

we don't need most of what's in components to be installed.
Much of it is included just for sdists or development.
we only install man pages to usr/share

let the function reflect this, rather than having several entries with no files.
only check for dependencies when installing without setuptools
fix missing-wheel command

because an empty distutils command must implement three no-op methods and one class attribute.

Which makes perfect sense.
validate package_data

and fix errors caught by the validation
font-awesome moved
make all of the extras lists

simpler, that way