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Amend Flamsteed constructor to accept and assign `u` and `uuid`
Rename Flamsteed `u` and `uuid` options
* Rename `u` to `session_id`
* Rename `uuid` to `fid`
* Support attribute aliases
* Update README
Amend README to include extra configuration example
Implement `schema` as event tag.
Implement `RUM` values simplification.
Implement `key` and `value` sanitisation.
Extend `serialise` test coverage
Amend README for performance timing metric changes
Merge pull request #9 from marckysharky/master

Page Impression Instance Amendments