Add config for Travis CI
Decrease required autotools version

for Travis CI build.
Require GCC/libstdc++ 4.8 in Travis build

Travis's default GCC version is 4.6, which is too old to build Sesh.
Disable dependency tracking in Jenkins build

Dependency tracking is unnecessary because everything is rebuilt in each
Jenkins build.
Merge pull request #29 from magicant/chore/travis

Update CI config for Travis and Jenkins