first pass at multisite.feature
don't test against WP 3.4.2 using PHP 5.4

It avoids this warning:

Creating default object from empty value in /wp-admin/includes/schema.php on line 922
test deleting a blog
add --porcelain flag to `blog create`
make `blog delete` accept a blog id as well
update man page for blog delete

[ci skip]
fix success message for `blog delete`
add 'Delete a blog by slug' scenario
Merge pull request #359 from wp-cli/test-multisite

Add tests for `wp blog`