Auto merge of #153 - servo:jdm-patch-2, r=asajeffrey

Use a more recent stable version of Rust.

This works around #152 by upgrading to a version of Rust that can build the most recent release of libz-sys.

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Author: bors-servo

.travis.yml

@@ -3,7 +3,7 @@ rust:
   - nightly
   - beta
   - stable
-  - 1.25.0
+  - 1.26.0
 sudo: 9000
 dist: trusty
 os: