Fixes #245.

- Added badges for issue count and repo stars
- Updated screenshots

Removed the link to nvmw project because it is no longer maintained.

Updated readme.md to make sure to remove the existing npm install location

Add a note to make sure the user removes any remaining nodejs installation directories before trying to use nvm-windows. Even running node's uninstaller before installing nvm-windows does not guarantee that this directory will be completely removed, and an nvm-generated symlink will not overwrite an existing installation directory.

Added note about iojs

Added thanks and alternatives.