Fix `Debug` output

[pczarn]

Found invalid Debug output in #89

[pczarn]

A contributor wants to work on this

[pczarn]

Work in #96

[pczarn]

@wyhaya

Two tasks left

• bit-set's Debug / Display https://github.com/contain-rs/bit-set
• adding _padding such as BitVec { storage: "11", _padding: "0000000000000000000", nbits: 2 }

[Jujumba]

• adding _padding such as BitVec { storage: "11", _padding: "0000000000000000000", nbits: 2 }

Is this still relevant? I can submit a PR for that

@pczarn