Fix: Bring back support for PHP 7.1

[localheinz]

This PR

• brings back support for PHP 7.1

Related to ergebnis/composer-normalize#266.

[codecov]

Codecov Report

Merging #191 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             master   #191   +/-   ##
=======================================
  Coverage       100%   100%           
  Complexity      128    128           
=======================================
  Files            30     30           
  Lines           379    394   +15     
=======================================
+ Hits            379    394   +15

Impacted Files	Coverage Δ	Complexity Δ
...Exception/SchemaUriCouldNotBeResolvedException.php	100% <0%> (ø)	2% <0%> (ø)	⬇️
...chemaUriReferencesInvalidJsonDocumentException.php	100% <0%> (ø)	2% <0%> (ø)	⬇️
...on/NormalizedInvalidAccordingToSchemaException.php	100% <0%> (ø)	2% <0%> (ø)	⬇️
src/Format/Formatter.php	100% <0%> (ø)	3% <0%> (ø)	⬇️
src/Exception/InvalidIndentStringException.php	100% <0%> (ø)	2% <0%> (ø)	⬇️
...eferencesDocumentWithInvalidMediaTypeException.php	100% <0%> (ø)	2% <0%> (ø)	⬇️
...rc/Exception/InvalidJsonEncodeOptionsException.php	100% <0%> (ø)	2% <0%> (ø)	⬇️
src/Exception/InvalidIndentSizeException.php	100% <0%> (ø)	3% <0%> (ø)	⬇️
...tion/OriginalInvalidAccordingToSchemaException.php	100% <0%> (ø)	2% <0%> (ø)	⬇️
src/Exception/InvalidJsonEncodedException.php	100% <0%> (ø)	2% <0%> (ø)	⬇️
... and 5 more

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