walk up directory tree to find config file

Allows WP-CLI to be invoked from anywhere within a project.
You are not limited to being in the directory where the wp-cli*.yml file is.
The DOCUMENT_ROOT is then set to the supplied path relative to the config file.
supply a default to the path config based on an upward search for wp-load.php

Add a Utils function for find_file_upward
Added behat feature for media regenerate
Regenerate Man
Added label to tax and cpt
Only preg_replace default $slug
prevent absolutizing a relative config path when it is empty

The result was that the config path was erroneously being set to the root /
This specifically happened when downloading WordPress via `wp core download`

See comment by @scribu: https://github.com/wp-cli/wp-cli/pull/362#issuecomment-15480546
deb-build: add sudo where appropriate

see #368
use MYSQL_PWD env variable in FeatureContext->run_sql()
add some functional tests for `wp db`
use MYSQL_PWD env variable, instead of passing the password as a CLI
arg
Merge pull request #369 from wp-cli/fix-mysql-warning

Warning: Using a password on the command line interface can be insecure
bump version to 0.9.1-alpha
Merge pull request #366 from linepress/media-tests

Added behat feature for media regenerate
handle edge case finding wp-cli.yml in nested subdirectory installs

See comment by @scribu: https://github.com/wp-cli/wp-cli/pull/362#issuecomment-15506011
use slug as theme name. closes #372
set version to 0.9.1
update-phar: OSX doesn't ship with md5sum, so use md5 -r
manpages: check for ronn executable before doing anything
document --force parameter for wp core download