add Build-Matrix

[mimmi20]

This PR wants to add a Build-Matrix to make the travis file more readable and group the tests.

As a result

• as first step the composer.json and composer.lock are validated
• as second step the coding style is checked
• for each PHP version the project is installed with lowest and normal dependency versions
• for each PHP version PHPUnit is run without XDebug to make the tests faster
• an additional test is run on the nightly build of PHP without dependency limits
• as last step PHPUnit is run with XDebug

This PR is related to PR #1129.

[siad007]

Please add --config-set ignore_warnings_on_exit 1 to avoid the build to fail on warnings.

[mimmi20]

I would prefer the -n option as it was before.

[codecov]

Codecov Report

Merging #1136 into master will decrease coverage by 1.38%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master    #1136      +/-   ##
============================================
- Coverage     47.02%   45.63%   -1.39%     
  Complexity     9968     9968              
============================================
  Files           505      505              
  Lines         24489    24416      -73     
============================================
- Hits          11515    11143     -372     
- Misses        12974    13273     +299

Impacted Files	Coverage Δ	Complexity Δ
classes/phing/util/PearPackageScanner.php	0% <0%> (-80.54%)	37% <0%> (ø)
classes/phing/types/PearPackageFileSet.php	0% <0%> (-79.49%)	13% <0%> (ø)
...g/tasks/ext/PhpCodeSnifferTaskFormatterElement.php	0% <0%> (-70.59%)	10% <0%> (ø)
...es/phing/tasks/system/condition/IsSetCondition.php	0% <0%> (-62.5%)	3% <0%> (ø)
classes/phing/tasks/ext/PhpCodeSnifferTask.php	0% <0%> (-40.32%)	94% <0%> (ø)
classes/phing/tasks/system/PhpEvalTask.php	0% <0%> (-32.4%)	32% <0%> (ø)
...sses/phing/tasks/system/condition/AndCondition.php	83.33% <0%> (-16.67%)	3% <0%> (ø)
classes/phing/util/PathTokenizer.php	50% <0%> (-9.1%)	12% <0%> (ø)
classes/phing/TaskAdapter.php	52.17% <0%> (-8.7%)	9% <0%> (ø)
classes/phing/system/io/FileParserFactory.php	75% <0%> (-6.82%)	4% <0%> (ø)
... and 62 more

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[siad007]

@mimmi20 thanks!