prepare to publish on crates.io

[tzemanovic]

• switched to use all published deps
• updated zcash_encoding 0.2 -> 0.2.2 (https://github.com/zcash/librustzcash/blob/main/components/zcash_encoding/CHANGELOG.md and diff https://github.com/zcash/librustzcash/compare/zcash_encoding-0.2.0..zcash_encoding-0.2.2)
• removed WIP from readme
• updated some non-breaking changes
  • there are lots of breaking changes in incrementalmerkletree, we should probably look into updating this later (update incrementalmerkletree dep #90)
• bump version to 1.2.0 to be released
• update to redjubjub fork with MASP trusted setup constants

[murisi]

Looks good to me. Thanks!

[Rigorously]

This broke the Namada MASP Indexer due to the num-traits dependency namada-net/namada-masp-indexer#35

[sug0]

The masp indexer is still using the SDK tagged with v0.46.0. This PR shouldn't have broken the build of namada-masp-indexer. What it looks like might happened is num-traits upstream broke semver with a patch release, which are implicitly bumped...