Add method: create_ad_audience_with_pixel

[sdlong]

Usage:

1. Set account:

FacebookAds.access_token = '<ACCESS_TOKEN>' account = FacebookAds::AdAccount.find('< AD_ACCOUNT_ID >')

2. create ad_audience with pixel:

account.create_ad_audience_with_pixel(name: '< NAME >', pixel_id: '< PIXEL_ID >', event_name: '< EVENT_NAME >')

PS: Use standard event name only

• ViewContent
• Search
• AddToCart
• AddToWishlist
• InitiateCheckout
• AddPaymentInfo
• Purchase
• Lead
• CompleteRegistration

e.g. : account.create_ad_audience_with_pixel(name: 'order complated', pixel_id: '328989100788312', event: 'Purchase')

[coveralls]

Coverage decreased (-0.4%) to 67.939% when pulling 3513b28949cf338721cd17f48f5c8bb37857702b on superlanding:t205 into 8f681eb363e131e22d454e6eece5791ffaa67f76 on cte:master.

[coveralls]

Coverage decreased (-0.4%) to 67.939% when pulling 8f285b561f755513d1f46d5244560162b93fcd15 on superlanding:t205 into 8f681eb363e131e22d454e6eece5791ffaa67f76 on cte:master.

[cte]

Thanks for the PR.