Updated travis config

[Nyholm]

Follow symfony best practice.

This will also update our dependencies and make the tests support sf4

[codecov-io]

Codecov Report

Merging #90 into master will decrease coverage by 7.02%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master      #90      +/-   ##
============================================
- Coverage     35.23%   28.21%   -7.03%     
- Complexity      207      208       +1     
============================================
  Files            21       21              
  Lines           877      918      +41     
============================================
- Hits            309      259      -50     
- Misses          568      659      +91

Impacted Files	Coverage Δ	Complexity Δ
src/Factory/SessionHandlerFactory.php	0% <0%> (-100%)	2% <0%> (ø)
src/Factory/RouterFactory.php	0% <0%> (-75%)	3% <0%> (ø)
src/Factory/ValidationFactory.php	0% <0%> (-75%)	3% <0%> (ø)
src/Factory/DoctrineBridgeFactory.php	0% <0%> (-75%)	3% <0%> (ø)
src/Bridge/SymfonyValidatorBridge.php	0% <0%> (-17.65%)	6% <0%> (ø)
src/Cache/FixedTaggingCachePool.php	0% <0%> (-12.5%)	14% <0%> (ø)
src/Routing/CachingRouter.php	0% <0%> (-10.87%)	14% <0%> (ø)
...cyInjection/Compiler/DataCollectorCompilerPass.php	63.63% <0%> (-3.04%)	4% <0%> (ø)
src/DataCollector/ProxyFactory.php	88% <0%> (-0.47%)	7% <0%> (ø)
.../DependencyInjection/Compiler/CacheTaggingPass.php	100% <0%> (ø)	3% <0%> (ø)	⬇️
... and 4 more

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