add basepath support

[pmjones]

This should be a fix for #86 -- @harikt @pine3ree please review and comment.

Basically, you create a RouterFactory with the basepath you want; that would be the subdirectory in which the application lives. You can then add routes as normal, without having to specify the basepath prefix; the matcher will match properly, and the generator will generate paths with the basepath prefix in place.

[harikt]

good to have one more test with no index.php . So is /path/to/sub/foo/bar

[harikt]

Thank you @pmjones . This looks good to me.

[pine3ree]

Thank You @pmjones
Looks fine to me.
To be on the safe side i would add

//...
$this->basepath = rtrim($basepath, ' /');

to the Router constructor for handling params like '/path/to/sub/'

[pmjones]

Added a dir-only test, and added rtrim. When the CI passes, I'll merge it. Thanks guys!