Update links to point to preservim

Change example to overwrite existing command, fixes #17

Added reference to new vim-wordchipper plugin

Link added for #13

Merge pull request #8 from somini/master

Check for special buffers

Merge pull request #7 from alem0lars/master

Fix typo in comment

Fix spellfile configuration example

Mention of default Vim mapping for terminal users

Merge pull request #2 from wikimatze/master

Update README

Add spellfile support

Make docs more consistent with my other plugins

plug of new vim-one project