tweak travis

.travis.yml

@@ -2,15 +2,6 @@ language: rust
 env:
   global:
     - secure: LhiHXBKaxsubX45eMukb39IDKaM0mdMzE8Ow4DCnq/yFTZn22ju/H3nMawk0X74gCMXsrADErcBke/7+mHV5GgToqtKjr8RaZDwAmZtzDgdrvJlqy+w59WbvJKuPXYGN0dPiVSkt/fFGf7qGFjLj0DiGZHw05XmBSq+90Qn3Iqw=
-  matrix:
-    - LLVM_VERSION=3.4
-    - LLVM_VERSION=3.5
-before_install:
-  - yes | sudo add-apt-repository "deb http://llvm.org/apt/precise/ llvm-toolchain-precise-${LLVM_VERSION} main"
-  - yes | sudo add-apt-repository "deb http://ppa.launchpad.net/ubuntu-toolchain-r/test/ubuntu precise main"
-  - sudo apt-get update
-install:
-  - sudo apt-get install --force-yes libclang-${LLVM_VERSION}-dev
 script:
   - export LD_PRELOAD=/usr/lib/llvm-${LLVM_VERSION}/lib/libclang.so
   - cargo build -v