Remove dev-dependencies features from serde_test

Apparently Cargo is applying these features to the non-dev dependency on
serde as well. Concluded by running `cargo clean && cargo build` and
observing that serde_derive was getting built.

.travis.yml

@@ -9,7 +9,7 @@ matrix:
         - cargo build --no-default-features
         - cd "${TRAVIS_BUILD_DIR}/serde_test"
         - cargo build
-        - cargo test
+        - cargo test --features serde/derive,serde/rc
 
     - rust: beta
       script:

serde_test/Cargo.toml

@@ -15,7 +15,7 @@ include = ["Cargo.toml", "src/**/*.rs", "crates-io.md", "README.md", "LICENSE-AP
 serde = { version = "1.0.60", path = "../serde" }
 
 [dev-dependencies]
-serde = { version = "1.0", path = "../serde", features = ["rc", "derive"] }
+serde = { version = "1.0", path = "../serde" }
 serde_derive = { version = "1.0", path = "../serde_derive" }
 
 [badges]