Update Cargo.toml to use semver compatibility for dependencies

[chantra]

Currently, dependencies are hardcoded with upper bounds. In some cases, it creates depedency issues as shown in #39.

This change removes the upper-bound and instead let rust rely on SemVer compatibility (https://doc.rust-lang.org/cargo/reference/resolver.html#semver-compatibility) as explained in https://doc.rust-lang.org/cargo/reference/specifying-dependencies.html#specifying-dependencies-from-cratesio