Add disable_test_ipv6 feature

This disables IPv6 tests. Meanly aimed at Travis, since it doesn't
support IPv6.

.travis.yml

@@ -17,4 +17,4 @@ rust:
 script:
   - cargo --version
   - rustc --version
-  - cargo test --verbose
+  - cargo test --verbose --features disable_test_ipv6

Cargo.toml

@@ -23,3 +23,7 @@ log      = "0.4.6"
 
 [dev-dependencies]
 env_logger = "0.6.0"
+
+[features]
+# Travis doesn't support IPv6, so we disable the tests for it.
+disable_test_ipv6 = []

tests/tcp_listener.rs

@@ -47,6 +47,7 @@ fn tcp_listener() {
 }
 
 #[test]
+#[cfg(not(feature="disable_test_ipv6"))]
 fn tcp_listener_ipv6() {
     let (mut poller, mut events) = init_with_poller();
 

tests/tcp_stream.rs

@@ -61,6 +61,7 @@ fn tcp_stream() {
 }
 
 #[test]
+#[cfg(not(feature="disable_test_ipv6"))]
 fn tcp_stream_ipv6() {
     let (mut poller, mut events) = init_with_poller();