fix travis setup problem

[dbu]

travis fails with "no output in the last 10 minutes". in the past, the problem was that there are too many versions of symfony that composer considers and it gets slow. as the tests already lock to symfony 2.6 i don't know if its the same issue. maybe we simple need to increase that timeout.

[dantleech]

This seems to be a general problem: composer/composer#4121
/cc @lsmith77

[lsmith77]

add sudo: false to your .travis.yml file

[dantleech]

Seems no longer to be an issue, closing.