Improved OpenRTB parsing of geo object to rtbkit::bidrequest to handle information from both device and user

Make GEO object in user optional

Populate the bid_request locaiton from the user.geo object if the values are present and only if empty in device.geo
AdMarkup is not required by nexage to be present in adm attribute, only that it is non empty
Merge pull request #187 from alkhatib/master

Nexage does not require adm to contain macro