Merge pull request #6 from bootleq/master

Refactor.
Fix augroup bug.

Keep fun, endf usage.
Fix: No write permissions in $VIMRUNTIME

$VIMRUNTIME is the installation directory. There is a big chance, that the user has no privileges to write to $VIMRUNTIME\session on modern Windows systems. Use $HOME\vimfiles\session instead.
Merge pull request #10 from niun/patch-1

Fix: No write permissions in $VIMRUNTIME