add serde to travis

.travis.yml

@@ -5,10 +5,16 @@ rust:
   - nightly
 
 env:
-  - ARCH=x86_64
-  - ARCH=i686
+  - ARCH=x86_64 FEATURES=''
+  - ARCH=i686 FEATURES=''
+  - ARCH=x86_64 FEATURES='serde'
+  - ARCH=i686 FEATURES='serde'
 
 addons:
   apt:
     packages:
       - gcc-multilib
+
+script:
+  - cargo build --verbose --features "$FEATURES"
+  - cargo test --verbose --features "$FEATURES"

Cargo.toml

@@ -13,7 +13,7 @@ keywords = ["stats", "mean", "skewness", "kurtosis", "quantile"]
 [dependencies]
 conv = { version = "0.3", default-features = false }
 quickersort = "3"
-serde = { version = "1", default-features = false, optional = true, features = ["derive"]}
+serde = { version = "1", optional = true, features = ["derive"]}
 
 [dev-dependencies]
 bencher = "0.1"