now absolutizing relative paths before sending them via uniqe

*   relative paths sent via libunique will not work in most cases,
    because the CWD will be different
*   added `luakit.absolutize` function to convert relative paths to
    absolute ones
*   checking if URI is file path and converting it to absolute before
    sending it through libuniqe
Store session in data directory instead of cache directory

As per XDG spec: cache dir is only for non-essential files.
Merge branch 'develop' into rel-paths

Conflicts:
	clib/luakit.c
fixed bug that prevented the usage of the non-fast loading
Escape mkdir paths
mkdir format should use rstring.format
Add visible property to all gtk widgets
Use new LUAKIT_WIDGET_SIGNAL_COMMON macro for focus/parent-set sigs
Add bindings for webkit web inspector (thanks Fabian!)
Stop repeating ourselves, use GOBJECT_TO_LUAKIT_WIDGET macro
Whoops GTK_WIDGET_VISIBLE has been deprecated since GTK 2.20
Pass widget_t* object to widget index/newindex functions
Fix URL in comment
Merge pull request #53 from Dieterbe/xdg

Store session in data directory instead of cache directory
Merge pull request #38 from karottenreibe/rel-paths

now absolutizing relative paths before sending them via uniqe
Removed individual glib header includes (no longer supported)
Removed unused awesomewm functions from luah.c
luakit.absolutize() -> os.abspath()
Update webkitgtk properties documentation link.
Link directly to WebKitWebSettings page.