Add support for Project.toml

Also:
-Deprecate REQUIRE file.
-Remove support for Julia < 1.0.

Julia 1.0 release

Renamed axes -> paxes to avoid issues.

Name paxes is unique, allowing the use of an empty signature (paxes()) without dispatch/abiguity issues.

Migrate to Julia v0.7

v0.3.0

Run tests on Julia 1.0.