transparently convert from --json to --format=json
option: add tests
post-meta: add tests
add --format parameter to meta get and update
save parent class in Subcommand

ReflectionMethod only stores the name of the original class, which might
be abstract.
unlike `wp option`, `wp post-meta` outputs confirmation messages
behat: work around bug in WP 3.4.2 related to serializing custom fields
behat: formatting fixes
user-meta: add tests
re-generate man pages

[ci skip]
unset 'json' key, not 'ids'
Merge pull request #459 from wp-cli/json-format

Convert from --json to --format=json