Remove composer.lock when running Travis.
Remove composer.lock when running Travis.

tonicospinelli/firefly-iii,firefly-iii/firefly-iii,tonicospinelli/firefly-iii,tonicospinelli/firefly-iii,JC5/firefly-iii,firefly-iii/firefly-iii,firefly-iii/firefly-iii,JC5/firefly-iii,tonicospinelli/firefly-iii,firefly-iii/firefly-iii