removed executable() check so as to support different perl versions using perlbrew (I.e. local version different to system version) via "let g:syntastic_perl_interpreter=/usr/bin/env perl"
Merge pull request #875 from colinmkeith/syntaxchecker_yamlxs

Support for perlbrew.

Remove executable() checks so as to support things like `let g:syntastic_perl_interpreter='/usr/bin/env perl'`.