Bump MSRV to 1.30.0

We wanted to bump to 1.29 to continue to support mrustc bootstrapping, but on 1.29
there's a bug preventing us from compiling the lightning package only, thus parts
of lightning-net-tokio cause a compilation error.

The advantage of bumping the MSRV is an improved borrow checker which should
enable improved code quality, and not having jump through weird hoops sometimes
to get 1.22 working.

.github/workflows/build.yml

@@ -8,8 +8,8 @@ jobs:
       matrix:
         toolchain: [ stable,
                      beta,
-                     # 1.22.0 is MSRV for rust-lightning in general:
-                     1.22.0,
+                     # 1.30.0 is MSRV for Rust-Lightning
+                     1.30.0,
                      # 1.34.2 is Debian stable
                      1.34.2,
                      # 1.39.0 is MSRV for lightning-net-tokio and generates coverage

.travis.yml

@@ -2,8 +2,8 @@ language: rust
 rust:
   - stable
   - beta
-  # 1.22.0 is MSRV for rust-lightning in general:
-  - 1.22.0
+  # 1.30.0 is MSRV for rust-lightning in general:
+  - 1.30.0
   # 1.34.2 is Debian stable
   - 1.34.2
   # 1.39.0 is MSRV for lightning-net-tokio and generates coverage

CONTRIBUTING.md

@@ -50,7 +50,8 @@ be covered by functional tests.
 When refactoring, structure your PR to make it easy to review and don't
 hestitate to split it into multiple small, focused PRs.
 
-The Minimal Supported Rust Version is 1.22.0 (enforced by our Travis).
+The Minimal Supported Rust Version is 1.30.0 (enforced by our Travis and
+GitHub Actions).
 
 Commits should cover both the issue fixed and the solution's rationale.
 These [guidelines](https://chris.beams.io/posts/git-commit/) should be kept in mind.