Provide a version in .info

Have the dev version information in the .info file so that modules can still be enabled when they have (2.x) in their information file. This just helps with working with git checkouts of the module. Very minor point, and doesn't affect any users. Just helps developers who checkout with git, and then are working with drush... Yeah, useless, but helpful to lazy people like me.

The actual version number gets overriden when it's packaged by Drupal.org.

Example:

name = xCSS
description = Empowers a straightforward and object-oriented workflow when developing complex CSS.
core = 7.x
dependencies[] = libraries (2.x)

Without 7.x-2.0-dev defined in libraries.info, when you have a git checkout of Libraries, you can't enable the xCSS module.