Look for in-ns when determining buffer namespace

Closes #19.

plugin/foreplay.vim

@@ -790,6 +790,14 @@ function! s:tons(path) abort
 endfunction
 
 function! foreplay#ns() abort
+  let lnum = 1
+  while lnum < line('$') && getline(lnum) =~# '^\s*\%(;.*\)\=$'
+    let lnum += 1
+  endwhile
+  let ns = matchstr(getline(lnum), '\C^(in-ns ''\zs\k\+\ze)')
+  if ns !=# ''
+    return ns
+  endif
   let path = s:buffer_path()
   return s:tons(path ==# '' ? 'user' : path)
 endfunction