For some reason the statusline doesn't always get redrawn automatically
after setting the statusline property for a window, and running
:redrawstatus when a buffer or window is entered seems to resolve this
issue.
Each window is now tagged with an UUID and this UUID is used to cache
the window's statusline contents in the Python VimRenderer in order to
avoid translating the statusline contents to and from a vimdict
unnecessarily.
Refs #11.
When Powerline is installed as a package in the system-wide
site-packages folder it can easily be enabled by adding a simple python
statement to the user's vimrc file.
Otherwise it can be added by doing a :source
path/to/plugin/vim/powerline.vim in vimrc, but the other way of doing it
works without specifying the full path as long as Powerline is installed
somewhere in sys.path.