New release with updated dependencies or less strict version ranges

[jhorstmann]

I tried updating dependencies in a cargo project and ran into an issue with a transitive dependency on once_cell = "1.2.*". Assuming once_cell correclty follows semantic versioning, the newer version 1.3.x or 1.4 should be compatible. Or was there a specific breaking change that requires staying with 1.2?

error: failed to select a version for `once_cell`.
    ... required by package `futures-task v0.3.5`
    ... which is depended on by `futures-util v0.3.5`
    ... which is depended on by `xxxxx`
versions that meet the requirements `^1.3.1` are: 1.4.0, 1.3.1

all possible versions conflict with previously selected packages.

  previously selected package `once_cell v1.2.0`
    ... which is depended on by `antlr-rust v0.1.1`
    ... which is depended on by `yyyyy`
    ... which is depended on by `xxxxx`

failed to select a version for `once_cell` which could resolve this conflict

[rrevenantt]

I think i just initially set it to 1.2 because back then I didn't know a lot about how versioning works in rust. Changing it to ^1.2 shouldn't be a breaking change, so I will do it for next versions.

[jhorstmann]

@rrevenantt Do you have any plans when the next version might be released? Or would you be interested in a pull request that just bumps dependencies to the newest version?