Laravel Localize Middleware Versions Save

Various small fixes and tidying up:

• Fixes README formatting (#6), and makes a few small other README updates
• Fixes issue with stack determiner fallback on Laravel 5.3/5.4 (#7)
• Fixes incorrect documentation for the parameter determiner (now correctly documented as request parameter rather than route parameter)
• Updates TravisCI to test against individual Laravel version
• Tidies up tests

This release adds functionality that allows you to specify a 'stack' of drivers, which will attempt to determine the locale sequentially. See the readme for more info.

Also:

• Determiners have been refactored internally to make adding new ones a bit easier
• phpdoc has been tidied up
• There've been a few more tweaks to tidy the codebase

• Add a determiner for setting the locale from a request header, which defaults to Accept-Language

Initial release