add travis CI config

[abacaphiliac]

apologies if this request seems forward. i'm not familiar with circle CI but i know travis pretty well. i'm interested in testing the dependency ranges in the CI build and i know how to do that in travis. if there is some documentation you can point to for how to accomplish this in circle CI i would be happy to give it a try : )

add travis config to test PHP versions 5.5 to 7.1. each PHP version is tested with the minimum and maximum dependency versions which provides some certainty that our dependency ranges in the composer config are valid.

here's a sample of the build output on my fork:
https://travis-ci.org/abacaphiliac/php-client/builds/184626287

[abacaphiliac]

i'm also interested in getting the integration tests running in CI. i know i can set up some services in travis via docker containers. is there similar support in circle?

[drichelson]

@abacaphiliac I like the idea. We do something similar for our python sdk. Are you aware of a tool similar to pyenv for php?

[abacaphiliac]

@drichelson cool! umm, maybe phpbrew, which i think this project uses in its Vagrant bootstrap. would you like me to take a crack at redoing this purely in Circle CI?

[drichelson]

@abacaphiliac Yeah that would be great! I changed the CircleCI setting for this repo so it should be building your commits on this forked repo for this PR. If not, please let me know.

[abacaphiliac]

@drichelson thank you! i tried getting Circle CI to run on my fork a few days ago but had no success. here is some sample output: https://circleci.com/gh/abacaphiliac/php-client/6

seems like maybe i need to set up a machine in my Circle account. any sage words of wisdom for a n00b?

[drichelson]

@abacaphiliac Try using the php version I now have set in our master branch: 5.6.17 and make sure you're using the ubuntu 14 image

[abacaphiliac]

hi @drichelson . i am able to run the Circle builds now. thank you for your assistance. i posted two competing solutions in Circle. they get the job done, but they run a little long for my taste and i'm sure we can optimize them. one uses phpbrew but the installations take forever, and the other uses docker. i favor the docker solution but the commands in both solutions are pretty verbose. i do appreciate the terseness and matrix-parallelization offered by Travis. please let me know what you think. if you're up for it, i think there would be no harm in using both Circle and Travis to accomplish different goals.

[abacaphiliac]

closing in favor of #51