Switch to Project.toml

[alyst]

Switch from REQUIRE to Project.toml generated by gen_project.jl script.
The package version is bumped to v0.5.0 since it requires Julia >= v1.0.3 (some compiler fixes), and v0.4.0 required Julia v0.7.

After this PR is merged, commenting on the head commit of the master branch (@ instead of @_) with

@_JuliaRegistrator register

Release notes:
<some release notes>

would automatically create new version PR to JuliaRegistry. Once it's merged, JuliaTagBot would tag a new BBO version and create the corresponding github release with the provided release notes.

Closes #127

[coveralls]

Coverage decreased (-0.1%) to 63.003% when pulling fb58af4 on alyst:toml_switch into 453f69d on robertfeldt:master.

[alyst]

This should be ready to merge.

P.S. Strangely, I don't see the CI (Travis) references in the PR status box (just above the message box), only the "no conflicts with the base branch".
Does it have anything to do with the repository settings?