switch working directory to buffer's folder

Fixes #36. Also, fixes a bug in Vim8 where we called the wrong method on
chdir.

Author: euclio

after/ftplugin/markdown/composer.vim

@@ -134,12 +134,14 @@ endfunction
 
 function! s:chdir()
   if exists('s:job')
+    let l:cwd = expand('%:p:h')
+
     if has('nvim')
-      call rpcnotify(s:job, 'chdir', getcwd())
+      call rpcnotify(s:job, 'chdir', l:cwd)
     else
       call ch_sendexpr(s:job, {
-            \ 'method': 'open_browser',
-            \ 'params': [getcwd()],
+            \ 'method': 'chdir',
+            \ 'params': [l:cwd],
             \ })
     endif
   endif

src/main.rs

@@ -134,8 +134,10 @@ fn read_rpc<R>(reader: R, browser: &Option<String>, handle: &mut Listening) wher
                 open_browser(&handle.http_addr().unwrap(), &browser);
             },
             "chdir" => {
-                handle.change_working_directory(rpc.params[0].clone());
-            },
+                let cwd = &rpc.params[0];
+                info!("changing working directory: {}", cwd);
+                handle.change_working_directory(cwd);
+            }
             method => panic!("Received unknown command: {}", method),
         }
     }