fixup!(v0.2.5): reinterpret --version/-V to show cargo-pretty-test version

[zjp-CN]

Note: cargo instead of cargo test supports that argument

before this PR

$ cargo pretty-test --version
Error from cargo-pretty-test:
"" should contain `running (?P<amount>\d+) tests?` pattern

Error from cargo test:
error: unexpected argument '--version' found

  tip: a similar argument exists: '--verbose'

Usage: cargo test --verbose... [TESTNAME] [-- [args]...]

For more information, try '--help'.

after this PR

$ cargo pretty-test --version
cargo-pretty-test version: 0.2.5

ref #23

[zjp-CN]

Already published cargo-pretty-test v0.2.5 at registry crates-io