When a file doesn't have a filetype, closer#enable is not called

[toniz4]

When a file with no file type (when not opening a file with no supported syntax, or not opening a file) closer#enable is not called. That makes it don't make the <CR> bind, in the case that g:closer_no_mappings is unset, or when it is set, binds that use <Plug>CloserClose will be treated as a string and will be printed to the file.

This will be solved by just calling closer#enable at plugin/closer.vim, instead of just making a autocmd for all filetypes.

Sorry for spamming issues, i just really liked this plugin and happened to found some little bugs. Thanks!