.travis.yml: Build-test on Rust 1.10

Document the distinction between full support and minimum support in
README.md.

Author: joshtriplett

.travis.yml

@@ -3,9 +3,11 @@ rust:
 - stable
 - beta
 - nightly
-# Oldest supported version.
+# Oldest supported version for all features.
 # Use of https://github.com/rust-lang/rfcs/pull/16
 - 1.13.0
+# Oldest supported version as dependency, with no features, tests, or examples.
+- 1.10.0
 
 sudo: false
 cache: cargo
@@ -22,8 +24,8 @@ before_script:
   export PATH=$HOME/.local/bin:$PATH
 
 script:
-- cargo build --verbose $FEATURES
-- cargo test --verbose $FEATURES
+- travis-cargo build -- $FEATURES
+- travis-cargo --skip 1.10.0 test -- $FEATURES
 
 after_success:
 - travis-cargo --only stable doc
@@ -32,6 +34,12 @@ after_success:
 env:
   global:
   - secure: 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
+  - TRAVIS_CARGO_NIGHTLY_FEATURE=""
   matrix:
   - FEATURES=--features=backtrace
   - FEATURES=--no-default-features
+
+matrix:
+  exclude:
+  - env: FEATURES=--features=backtrace
+    rust: 1.10.0

README.md

@@ -28,6 +28,9 @@ to error-chain.
 Please view the beginning of the [Travis configuration file](.travis.yml)
 to see the oldest supported Rust version.
 
+Note that `error-chain` supports older versions of Rust when built with
+`default-features = false`.
+
 ## License
 
 MIT/Apache-2.0