use Travis CI

- use clang 3.5 for C++14
- I can't found how to use gcc 4.9 on Ubuntu 12.04 without building it

add config for Travis CI

authenticate LLVM packages

link Boost.Test

fix command

use the latest gcc

clear away a.out

fix package name of gcc snapshot

fix command of g++ snapshot

tmp

use ppa again

remove gcc because version of gcc is too old.

tiny improvements

clang-3.4 package doesn't exist

tiny cosmetic change

add ppa repository