Add MSRV 1.31.0 to CI

.travis.yml

@@ -32,6 +32,23 @@ matrix:
       rust: nightly
       if: (branch = staging OR branch = trying) OR (type = pull_request AND branch = master)
 
+    # MSRV
+    - env: TARGET=x86_64-unknown-linux-gnu
+      rust: 1.31.0
+
+    - env: TARGET=thumbv7m-none-eabi
+      rust: 1.31.0
+      if: (branch = staging OR branch = trying) OR (type = pull_request AND branch = master)
+
+    - env: TARGET=thumbv7em-none-eabi
+      rust: 1.31.0
+      if: (branch = staging OR branch = trying) OR (type = pull_request AND branch = master)
+
+    - env: TARGET=thumbv7em-none-eabihf
+      rust: 1.31.0
+      if: (branch = staging OR branch = trying) OR (type = pull_request AND branch = master)
+
+
 before_install: set -e
 
 install:

README.md

@@ -6,6 +6,11 @@ This project is developed and maintained by the [Cortex-M team][team].
 
 ## [Documentation](https://docs.rs/panic-itm)
 
+## Minimum Supported Rust Version (MSRV)
+
+This crate is guaranteed to compile on stable Rust 1.31.0 and up. It *might*
+compile with older versions but that may change in any new patch release.
+
 ## License
 
 Licensed under either of