Two reasons here:
1) Ubuntu Precise is reaching EOL, though Travis CI may take care of it.
we still can move to Trusty earlier as I didn't see any dependency of
Precise here.
2) g++4.8 is built-in in Travis CI's Ubuntu Trusty environment, which
means we don't need to spend time on adding ppa repository, apt update
and apt install, could save time on the CI.
1. Remove eslint , bacause we use JavaScript Standard Style.
2. Add lts/boron version to travis CI, web use it in docker version
Signed-off-by: BoHong Li <a60814billy@gmail.com>
