fix sign overwriting regex

Signs (from Syntastic in this case) were overwritten, although
g:signify_sign_overwrite was set to 0, because the used regex was buggy.

Add Ryan Kois as contributor.

Closes #20.

doc/signify.txt

@@ -275,6 +275,7 @@ fritzophrenic     (fritzophrenic)
 Morgan Fouesneau  (mfouesneau)
 Zhao Cai          (zhaocai)
 Otto Modinos      (otommod)
+Ryan Kois         (kid-icarus)
 
 
 ==============================================================================

plugin/signify.vim

@@ -194,8 +194,8 @@ function! s:sign_get_others(path) abort
     silent! execute 'sign place file='. a:path
   redir END
 
-  for line in filter(split(signlist, '\n'), 'v:val =~ "\v^\s+\w+"')
-    let lnum = matchlist(line, '\v^\s+\w+\=(\d+)')[1]
+  for line in filter(split(signlist, '\n'), 'v:val =~ "^\\s\\+line"')
+    let lnum = matchlist(line, '\v^\s+line\=(\d+)')[1]
     let s:other_signs_line_numbers[lnum] = 1
   endfor
 endfunction