add docker feature

[amltv]

also add .gitattributes to exclude some dev requirements

[coveralls]

Coverage remained the same at 100.0% when pulling 1992a05 on justcontrol-it:feature-docker into a71a451 on the-tinderbox:master.

[evsign]

Thanks for the pr!
I don't fully understand what is this for. I assume this is for more easy local development and ci? If this it, can you add readme section about using it and changes to the .travis.yml please?

[amltv]

Yes, docker needed for easy local development. Our teem use this lib, and we planned push new PR soon, docker help us this it.
Sure, I add readme section. and change travis

[amltv]

• added xdebug, needed for coverage.
• change docker-compose for ci compatibility.
• add how to run tests with Docker

Please check that travis work perfect, i cant check them!!

P.S. try use phpunit/phpunit docker image but, ccat not work in container. I think it because image based on Alpine