Add PHP7 for travis

[indytechcook]

[k-k]

@indytechcook - I think its safe to set the php version to >=5.4

[indytechcook]

Sorry to make the commit log messy.

[k-k]

No worries, you can always rebase to clean up the commits if it bothers you.

I tried rebuilding the test on travis - it seems like its ignoring the recent composer.json change.

[indytechcook]

I tried to run composer update to see if travis just looks at the lock file but ran into another dependency issue:

  Problem 1
    - Installation request for mockery/mockery dev-master -> satisfiable by mockery/mockery[dev-master].
    - mockery/mockery dev-master requires hamcrest/hamcrest-php ^2.0@dev -> no matching package found.

[k-k]

oh jeez. never meant to include the lock file in the first place. feel free to nuke that.

Should be able to fix the dependencies by fixing the versions on a couple of those dev dependencies:

"mockery/mockery":    "~0.9.4",                                         
"phpunit/phpunit":    "~4.0",                                           
"raulfraile/ladybug": "~1.0.13" 

[k-k]

let me know, I don't mind doing a separate PR to fix those issues