Revert "Ensure WithdrawState windows stay unmapped on restart"

This reverts commit c8eda724dfabfa5288b56ffdd084a4765561813d.

There might (?) be a problem with this, so reverting temporarily before 0.7.0
is tagged.
Merge branch 'develop' into master
Release 0.7.0
Clean up documentation headers

Some day I will get all this right. Some day.
Correct a small mistake on README.rst
New debuginfo widget to help qtile debug.

  Shows focused window's index, stack or section index ...
  Supports only TreeTab and Stack layouts for now but more will follow.

  Closes #401
Add autosplit parameter to stack layout

  Disabled by default, it makes all stacks
  splitted by default.
Add previous_on_rm param to TreeTab layout

Makes previous window selected on remove instead of first.
Default value: False
Rearrange config options

* stacks argument is now num_stacks to avoid conflict
* several arguments from recent PRs merged to defaults framework

Closes #400
Closes #398
Bind a shutdown key in the default config
new widget: a launchbar

... with icons to click to launch a software or to execute a qtile python
instruction (like for login out, see example in code)

Closes #397
Shutdown qtile on XCB fatal connection errors
launchbar requires xdg

We don't want users to have to install every dependency for every widget, so as
before, we just protect this by catching ImportError.
Fix some {Name,Attribute}Errors
add support to match wm_class instance in Match objects

the first string in WM_CLASS atom, is the instance class name
see 4.1.2.5. at http://tronche.com/gui/x/icccm/sec-4.html
bitcoin ticker widget uses btc-e instead of mt gox
Make layout.Max answer to _Group.cmd_{prev,next}_window()
Add bitcoin defaults in the right place
Allow passing SCREEN_SIZE to Xephyr and flags to qtile
Default to setuptools but don't fail if it's not available.

Closes #411