Merge tag '1.8.0' into develop

Release v1.8.0

Updated for 1.7.0 release.

Signed-off-by: Sacha Telgenhof <[email protected]>

Updated changelog to reflect fix for UK.

Added missing test suite for Romania.

PSR-2 fixes (causing Travis to fail).

Updated documentation for 1.4.0 release.

Updated documentation for 1.3 release.

Corrected release version number.

Removed PHP 5.4 support.

Added filters feature. Using Yasumi you can filter holiday providers …

…to only show official holidays, observed holidays, bank holidays, seasonal holidays or other type of holidays.