Add the phpunit requirement (build on travis with version 5.4.0)

[sseidelmann]

Hey everybody,

I want to add a feature and checked first the unit tests. I found no reference to used phpunit version. So i added it as a dev-requirement (version used from travis build).

Greetings

[acrobat]

Please use a version constraint that allows supported versions of phpunit. PHPUnit 4 is eol since 3 February 2017

It's better to use this constraint:
"phpunit/phpunit": "^5.5|^6.0"

[sseidelmann]

Thats right. i will check the dependency and update them.

[acrobat]

I think it's better to deprecate some old (and unsupported) php versions, instead of making workarounds for phpunit versions. I will open a PR later today to propose a fix!

[sseidelmann]

Jeah that will be great, i will wait for it

[lsmith77]

you also need to adjust the script in .travis.yml to use the composer installed phpunit

[acrobat]

@lsmith77 I've create PR #124 to bump to php version and require phpunit (+ test fixes).

[sseidelmann]

I close this PR