Fix running tests on on "stable" Rust

.gitignore

@@ -1,2 +1,4 @@
 target
 Cargo.lock
+
+/.idea/

.travis.yml

@@ -3,16 +3,18 @@ branches:
   - /.*(.tmp)$/
 
 language: rust
+env: EXTRA_ARGS="--features unstable"
 matrix:
   include:
     # This version is tested to avoid unintentional bumping of the minimum supported Rust version
     - rust: 1.20.0
+      # This version don't support unstable features
+      env: EXTRA_ARGS=""
     - rust: stable
     - rust: stable
       os: osx
     - rust: beta
     - rust: nightly
-      env: EXTRA_ARGS="--features unstable"
 
 sudo: false
 script:

test_suite/Cargo.toml

@@ -7,7 +7,7 @@ unstable = ["compiletest_rs"]
 
 [dependencies]
 bitflags = { path = "../" }
-compiletest_rs = { version = "*", optional = true }
+compiletest_rs = { version = "0.3.18", optional = true, features=["stable"] }
 serde = "1.0"
 serde_derive = "1.0"
 serde_json = "1.0"