pulled recurly-related code out of go-subscriptions into go-recurly

see https://github.com/GigaOM/legacy-pro/issues/4125
do not iterate over user's capabilities the user does not have it. (reduces php warnings)
check in generated css
Merge pull request #1 from wluo/freebird

Freebird: go-recurly
ported unit tests from go-subscriptions to go-recurly
fixed a call to go_subscriptions()->create_guest_user()
Merge pull request #2 from wluo/freebird

ported unit tests from go-subscriptions to go-recurly
consolidate go-recurly-freebies into go-recurly
clean up the created users after testing
Merge pull request #4 from wluo/freebird

clean up the created users after testing
refactor, per code review
Merge branch 'freebird' of github.com:GigaOM/go-recurly into freebird
code review fixes; remove extra admin call
Merge pull request #3 from okredo/freebird

consolidate go-recurly-freebies into go-recurly
submoduled the external recurly php client
Merge pull request #6 from wluo/freebird

submoduled the external recurly php client
responded to many code review comments plus some clean-up.
moved go-recurly-behavior.js to go-subscriptions (as go-subscriptions-sign-up.js)
* lazily instantiate GO_Recurly_Freebies
* moved subscription meta to go-recurly
* moved GO_Recurly_Freebies' config to GO_Recurly's
moved the invite() function from class-go-recurly-freebies.php to class-go-recurly-freebies-admin.php since it's only used by the admin class
more code review cleanups
fixed how we get the signup_action from GO_Recurly