Added workdir to wineexec

Might want to add it to execute() in installer.py but it's using
subprocess.call() which doesn't seem to have a working dir argument,
contrary to subprocess.Popen()
Fix: installed games getting the "not installed" banner style upon banner download

Note : I don't understand why you carry the is_installed variable
around in the args of many functions instead of getting/setting it
from the Game object.
Do not code without Flake8, ever
Fix TreeView sorting
Merge branch 'fix-sort-treeview' of git://github.com/Xodetaetl/lutris into Xodetaetl-fix-sort-treeview
Merge branch 'fix-not-installed' of git://github.com/Xodetaetl/lutris into Xodetaetl-fix-not-installed
Merge branch 'workdir' of git://github.com/Xodetaetl/lutris
Smaller banners on List View
Renamed ICON_SIZE to BANNER_SIZE
Add Year column

Though I have no idea how to update the local DB to
add the years.
Cleanup List view
Update icons to correct size depending on view

I'm not too sure about that part :
```
def update_image(self, game_slug, is_installed=False):
         row = self.get_row_by_slug(game_slug)
         if row:
-            game_pixpuf = get_pixbuf_for_game(game_slug,
+            game_pixpuf = get_pixbuf_for_game(game_slug,
self.icon_size,

is_installed=is_installed)
```
I'm calling icon_size from the parent class (GameView) of the class
where it's set (TreeView and IconView). It doesn't look right to me
but I don't know how to do it otherwise without duplicating
update_image() in each child class.
Bump version to 0.3.4
Fix date in changelog
Add 'format' option to extract installer task
Add documentation for format option
Update installers.rst

I said bullshit, I take it back.
Add 'path' option to wine games
Add 'Browse files' to contextual menu
Merge branch 'patch-2' of git://github.com/Xodetaetl/lutris