Force apt-get to do what I told it to do.

.travis.yml

@@ -5,12 +5,12 @@ compiler:
   - gcc
 
 before_install:
-  - sudo apt-get update
-  - sudo apt-get install tcl tcl-dev
-  - if [ "$CXX" = "g++" ]; then sudo apt-get install libcppunit-dev libcppunit-1.13-0; fi
-  - if [ "$CXX" = "g++" ]; then sudo apt-get install gcc-4.8 g++-4.8; fi
+  - sudo apt-get -y update
+  - sudo apt-get -y install tcl tcl-dev
+  - if [ "$CXX" = "g++" ]; then sudo apt-get -y install libcppunit-dev libcppunit-1.13-0; fi
+  - if [ "$CXX" = "g++" ]; then sudo apt-get -y install gcc-4.8 g++-4.8; fi
   - if [ "$CXX" = "g++" ]; then export CXX="g++-4.8" CC="gcc-4.8"; fi
-  - if [ "$CXX" = "clang++" ]; then sudo apt-get install clang-3.6; fi
+  - if [ "$CXX" = "clang++" ]; then sudo apt-get -y install clang-3.6; fi
   - if [ "$CXX" = "clang++" ]; then svn co --quiet --trust-server-cert --non-interactive https://llvm.org/svn/llvm-project/libcxxabi/trunk@r249649 libcxxabi; fi
   - if [ "$CXX" = "clang++" ]; then svn co --quiet --trust-server-cert --non-interactive https://llvm.org/svn/llvm-project/libcxx/trunk@r249595 libcxx; fi
   - if [ "$CXX" = "clang++" ]; then (cd libcxx/lib && env CXX="clang++ -I ../../libcxxabi/include" sh buildit); fi