Merge pull request #111 from jarstelfox/master

Add static type checking!

Merge pull request #97 from KartaviK/hotfix/enum-inheritance-compatib…

…ility

 Solution for construct enum from inherited enum with incompatible value

Merge pull request #89 from jmsfwk/reduce-php-version

Change minimum PHP version to 7.1

Add return type declaration for "equals()" method (#88)

Add return type declaration for "equals()" method

Merge pull request #84 from KartaviK/hotfix/ext-json-requirements

 Add ext-json to requirements for package

Merge pull request #83 from KartaviK/feature/envelope-enum-construct

 Create instance of enum from same enum in constructor

Merge pull request #82 from myclabs/fix-coding-style

Fix coding style

Merge pull request #78 from KartaviK/feature/nullable

Set opportunity to create enum statically with null value

Merge pull request #75 from willemstuursma/php-72-optimizations

Prefix all function calls with a backspace

Merge pull request #71 from osavchenko/allow_null_in_equals

allow null in equals