Use https for git instead of git protocol

git protocol port is not open on the new performance platform
infrastructure.
Merge pull request #13 from alphagov/https-pip-git

Use https for git instead of git protocol
Test multi value fields are kept as is
Map multi value field into individual elements
Unpack regexp into vars
Split multi value mapping to separate function
Extract multi value strins as variables
Handle invalid index and missing key
Update to include multi value field mapping
Split one to one mapping to separate function
Rename multi fields mapping method
Merge branch 'multi-value-fields' of github.com:alphagov/backdrop-ga-collector into multi-value-fields
Match beginning and end in regexp
Merge pull request #14 from alphagov/multi-value-fields

Multi value fields