Preview release with improved Query API, improved docs, other improvements

Incite library API improvements.

• Tentatively finalized file-scope Query function signature.
• Normalized some error edge cases and found and added some missing error edge cases.

Package and build improvements.

• Corrected the module minimum supported Go version (to 1.14).
• Added continuous integration with Travis.
• Fixed a couple of linting warnings.

Other improvements.

• Incrementally improved documentation.
• Incrementally increased test coverage.