Adding support for phpstan

Features:

• Adding phpstan validator

Changes:

• Removing php7.1 from support
• Cleaning up the project thanks to @lchrusciel

Fixes:

• Improving the documentation on how to extend the plugin
• Removing documentation for non-existing validators

Fixing shebang to run on travis

1.0.1

Improving shebang

First version of the package

In the current version of the package the package supports the following parsers:

• Markdown

And the following validators out of the box:

• XML
• PHP Linter
• PHP use statement validator

There are other parsers planned and also more validators.