Merge #295: Add Cargo-lockfile generation in README

3c97646 Add generate-lockfile to README (Aman Rojjha)

Pull request description:

  Previously, just version-pinning the dependencies were unable to generate the lockfile properly. Manually generating lockfile before the same works!

ACKs for top commit:
  apoelstra:
    ACK 3c97646

Tree-SHA512: e69033089c6d0ae0f79465a3fa7c60a243f66e0d76dc31a35d2e83e36650633a53e38133df76dfa2d92d83a7bc8243461523df741a7e32aa5e5caa5a3369ccfe

Author: apoelstra

README.md

@@ -38,9 +38,10 @@ or in [the `examples/` directory](https://github.com/apoelstra/rust-miniscript/t
 ## Minimum Supported Rust Version (MSRV)
 This library should always compile with any combination of features on **Rust 1.29**.
 
-Because some dependencies have broken the build in minor/patch releases, to
-compile with 1.29.0 you will need to run the following version-pinning command:
+Because some dependencies have broken the build in minor/patch releases, to compile with 1.29.0 you will need to
+generate the lockfile and run the following version-pinning command:
 ```
+cargo generate-lockfile --verbose
 cargo update -p cc --precise "1.0.41" --verbose
 ```