Made number_format behaviour on null argument compatible with Twig
#245 - Initial support for expression-based inclusions
Update .travis.yml
Merge pull request #254 from lyncodev/null-safe-number-format-250-master

[master] Made number_format behaviour on null argument compatible with Twig
Merge pull request #256 from thomas-p-wilson/fix-include-expression

#245 - Initial support for expression-based inclusions
Merge branch 'master' of github-personal:jtwig/jtwig into refactor-template-model

Conflicts:
	jtwig-core/src/test/java/org/jtwig/unit/content/model/IncludeTest.java