CEL Spec update to document heterogeneous equality, NaN, and ordering…

… updates (google#232)

Add string conversion for timestamp and duration to spec (google#195)

These are present in the conformance tests.

Add timestamp conversion to string test to ensure nanoseconds are pre…

…served (google#184)

Golang protobuf v2 API support (google#161)

Conformance tests for has() on messages. (google#116)

Update the bazel build rules_cc archive reference (google#86)

Release Notes v0.2.0

* New tests for time-related functions.
* Moved broken test to proper suites based on latest cel-go fixes.

Move fixed tests into their appropriate locations. (google#49)

Merge pull request google#9 from eobrain/master

Enable Travis continuous integration testing of proto files