Bump signature from 1.6.0 to 2.0.0

Bumps [signature](https://github.com/RustCrypto/traits) from 1.6.0 to 2.0.0.
- [Release notes](https://github.com/RustCrypto/traits/releases)
- [Commits](https://github.com/RustCrypto/traits/compare/signature-v1.6.0...signature/v2.0.0)

---
updated-dependencies:
- dependency-name: signature
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Cargo.lock

@@ -113,7 +113,7 @@ dependencies = [
  "serde_derive",
  "serde_json",
  "sha2 0.10.6",
- "signature",
+ "signature 2.0.0",
  "simplelog",
  "spmc",
  "sqlite",
@@ -470,7 +470,7 @@ version = "1.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4620d40f6d2601794401d6dd95a5cf69b6c157852539470eeda433a99b3c0efc"
 dependencies = [
- "signature",
+ "signature 1.6.4",
 ]
 
 [[package]]
@@ -1160,9 +1160,15 @@ dependencies = [
 
 [[package]]
 name = "signature"
-version = "1.6.0"
+version = "1.6.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f0ea32af43239f0d353a7dd75a22d94c329c8cdaafdcb4c1c1335aa10c298a4a"
+checksum = "74233d3b3b2f6d4b006dc19dee745e73e2a6bfb6f93607cd3b02bd5b00797d7c"
+
+[[package]]
+name = "signature"
+version = "2.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8fe458c98333f9c8152221191a77e2a44e8325d0193484af2e9421a53019e57d"
 
 [[package]]
 name = "simplelog"

Cargo.toml

@@ -21,7 +21,7 @@ ed25519-dalek = "1.0"
 x25519-dalek = "1.2"
 ecies-ed25519 = "0.5"
 chacha20poly1305 = "0.9.1"
-signature = "1.6"
+signature = "2.0"
 blakeout = "0.3.0"
 num_cpus = "1.13.1"
 byteorder = "1.4.3"