vimrc 7.x-1.0-alpha4

This release includes all the features added in 7.x-1.0-alpha3 and uses the experimental directory structure of 7.x-1.0-alpha1. From now on, it should be possible to install the project with drush:

$ drush dl @none vimrc
$ drush help vimrc-install
$ drush -v vimrc-install <options>

Upgrade note:

This release organizes files in the same way as the 7.x-1.0-alpha1 release, which is different from all previous versions. If you are upgrading from a previous version, please review the installation instructions.

New features since 7.x-1.0-alpha3:
#1145580: Add installer?
#1735030: Drush command to create your own tags file.

Bug fixes since 7.x-1.0-alpha3:
#1835658: OpenCommand() fails to return "open" using Mac-installed version of vim.
#1831502: More reliable detection of Drupal root directory
#1825224: t() snippet tab stop typo