Fix cache if URL has trailing slash

[howdu]

If the URL ends with a slash the explode contains an empty element at the end.

$segments = explode('/', ltrim($request->getPathInfo(), '/'));

Simple fix changing ltrim to trim

e.g: https://example.com/about-us/
VS: https://example.com/about-us

page-cache/about-us.html
page-cache/about-us/pc__index__pc.html

Nginx/apache will never read the latter.

Fixes issue: #35