Revert "travis: work around temporary test failure due to rustc crashing on hyper."

This reverts commit 326270a.

Author: matthiaskrgr

.travis.yml

@@ -63,8 +63,7 @@ matrix:
     - env: INTEGRATION=chronotope/chrono
     - env: INTEGRATION=serde-rs/serde
     - env: INTEGRATION=Geal/nom
-# uncomment once https://github.com/rust-lang/rust/issues/55376 is fixed
-#    - env: INTEGRATION=hyperium/hyper
+    - env: INTEGRATION=hyperium/hyper
   allow_failures:
   - os: windows
     env: BASE_TEST=true