Add an option to insert trailing line to comments

Fixes #10.
Introduced "trailing_empty_line" option
which adds possibility to insert trailing line into comments.
This option is off by default.
Rename "Default.sublime-keymap" to "Default (Windows).sublime-keymap"

This file could not be opened from main menu
Preferences -> Package Settings -> Sublime-Yardoc -> Settings - Default
due to this wrong name.

Renamed this file to "Default (Windows).sublime-keymap" because
Main.sublime-menu:42 referenced to it.
Merge branch 'trailing-empty-line'
Merge branch 'rename-keymap-file'