Fix documents and bencher_compat dep refer outdated criterion v0.4

[rhysd]

This PR fixes the following two issues:

• Documents including the quick start guide still use old criterion v0.4. When users refer them, they would accidentally use the old version instead of the latest v0.5.1
• criterion_bencher_compat depends on criterion crate v0.4. But the current version in the workspace is v0.5.1. So cargo check reports the following error

  error: failed to select a version for the requirement `criterion = "^0.4.0"`
  candidate versions found which didn't match: 0.5.1
  location searched: /path/to/criterion.rs
  required by package `criterion_bencher_compat v0.4.0 (/path/to/criterion.rs/bencher_compat)`