fix issue355: junitxml generates name="pytest" tag.
introduce yieldctx=True in the @pytest.fixture decorator. Refactor tests and docs.
don't manipulate FDs at all if output capturing is turned off.
rework docs to demonstrate and discuss current yield syntax in more depth.
remove gittip mention for now.
fix some tests wrt to expecting output now that pytest does no
introduce unwanted "buffering" on "-s" calls.
merge monkeypatch.replace into monkeypatch.setattr, also support monkeypatch.delattr.
bump version
re-order CHANGELOG and group it into "features" and "bugs" and "known incompatibilities"
is actually a new feature, the syntax: pytest.mark.parametrize("arg1,arg2", ...)
add terminalreporter.section|line methods to print extra information.
move FILE_OR_DIR constant out
simplify Config constructor
refine fromdictargs to avoid an uncessary re-setup of the pluginmanager
remove very likely unused pytest_plugin_unregister hook (pytest itself and all plugins i know don't use it)
introduce pluginmanager.ensure_teardown() which allows
avoid creation of file in os.getcwd() cc avanderneut
localize some argcomplete-related functionality
shift pytest_configure/unconfigure/addoption/namespace hook calling to config object.

The _pytest.config module itself is no longer a plugin but the actual
config instance is plugin-registered as ``pytestconfig``.
This allows to put most pytest specific logic to _pytest.config instead
of in the core pluginmanager.
some more separation of core pluginmanager from pytest specific functionality.
Idea is to have the PluginManager be re-useable from other projects at some point.