first pass at 'wp super-admin' commmand
wp user create: validate fields before calling wp_insert_user()

see #358
wp core install: validate admin email

closes #358
bump minimum required WP version to 3.5.2
Merge pull request #1004 from wp-cli/wp-3.5

Bump the minimum supported version of WordPress to 3.5
wp media regenerate: check if there is platform support for generating images before starting
check for platform support before calling 'wp media import' too
Merge pull request #1003 from wp-cli/img-ext-check

Check that php-gd or php-imagick is available, before calling `wp media regenerate`
support arbitrary command nesting
prevent registering subcommands for concrete commands
Merge pull request #1005 from wp-cli/fourth-level

Support arbitrary command nesting
generate bash completions unambiguously for fourth-level subcommands
complete with filenames for commands that have <file> in their synopsis
update Behat tests for completions
complete with command flags and associative parameters
remove conversion from 'wp --completions' to 'wp cli completions'

the format is different and associative parameters are required
Merge pull request #212 from wp-cli/completions-overhaul

Improve bash completions

fixes #547
fixes #994
bump version to 0.15-alpha
convert `wp *-meta` subcommands to `wp * meta`
pass full path to 'before_invoke:'