Better support for the spec

What's Changed

• Update README.md to use correct options - Project import generated by Copybara. by @VickSuresh in #8
• Implement Select() function by @VickSuresh in #11
• Implement Children() and Descendants() by @VickSuresh in #12

Full Changelog: v1.0.0...v1.1.0

Initial Version

This is the initial release of Verily's FHIRPath implementaton in Go.

This package contains a Go implementation of the FHIRPath specification, implemented directly with the google/fhir proto definitions.

This package aims to be compliant with both:

the N1 Normative Release specification, and
the R4 specifications.