428: Bump abci from 0.6.1 to 0.6.2 r=tomtau a=dependabot-preview[bot]

Bumps [abci](https://github.com/tendermint/rust-abci) from 0.6.1 to 0.6.2.
<details>
<summary>Changelog</summary>

*Sourced from [abci's changelog](https://github.com/tendermint/rust-abci/blob/develop/CHANGELOG.md).*

> ## v0.6.2
> 
> ### BREAKING CHANGES:
> 
> ### FEATURES:
> 
> ### IMPROVEMENTS:
> 
> ### BUG FIXES:
> -  [\#89](https://github-redirect.dependabot.com/tendermint/rust-abci/pull/89): Version of protobuf specified to the latest one (2.8.1)
> 
> *August 23, 2019*
> 
> Special thanks to external contributors on this release: [@&#8203;amanusk](https://github.com/amanusk), [@&#8203;marbar3778](https://github.com/marbar3778)
</details>
<details>
<summary>Commits</summary>

- See full diff in [compare view](https://github.com/tendermint/rust-abci/commits)
</details>
<br />

[![Dependabot compatibility score](https://api.dependabot.com/badges/compatibility_score?dependency-name=abci&package-manager=cargo&previous-version=0.6.1&new-version=0.6.2)](https://dependabot.com/compatibility-score.html?dependency-name=abci&package-manager=cargo&previous-version=0.6.1&new-version=0.6.2)

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</details>

429: Problem: no test of prefix merkle trie determinism r=tomtau a=tomtau

Solution: added a basic quickcheck property to check trie root after insertions in different order

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>
Co-authored-by: Tomas Tauber <2410580+tomtau@users.noreply.github.com>