Vundle messages improvements

* Lower the severity of some of the errors when they are not really
catastrophic.
* Mention Vundle in all messages
* Make some of the messages a little more specific

Closes #579

autoload/vundle/config.vim

@@ -98,13 +98,14 @@ endf
 funct! s:check_bundle_name(bundle)
   if has_key(s:bundle_names, a:bundle.name) &&
         \ s:bundle_names[a:bundle.name]['uri'] != a:bundle.uri
-    echoerr 'Vundle error: Name collision for Plugin ' . a:bundle.name_spec .
+    echomsg 'Vundle warning: Name collision for Plugin ' . a:bundle.name_spec .
           \ '. Plugin ' . s:bundle_names[a:bundle.name].spec .
           \ ' previously used the name "' . a:bundle.name . '"' .
           \ '. Skipping Plugin ' . a:bundle.name_spec . '.'
     return 0
   elseif a:bundle.name !~ '\v^[A-Za-z0-9_-]%(\.?[A-Za-z0-9_-])*$'
-    echoerr 'Vundle error: Invalid plugin name: ' . a:bundle.name
+    echomsg 'Vundle warning: Invalid plugin name: ' . a:bundle.name . 
+          \ '. Skipping Plugin ' . a:bundle.name_spec . '.'
     return 0
   endif
   let s:bundle_names[a:bundle.name] = { 'spec' : a:bundle.name_spec,

autoload/vundle/installer.vim

@@ -21,7 +21,8 @@ func! vundle#installer#new(bang, ...) abort
   let bundles = filter(copy(bundles), '!empty(v:val)')
 
   if empty(bundles)
-    echoerr 'No bundles were selected for operation'
+    let operation = a:bang ? 'update' : 'installation'
+    echomsg 'Vundle warning: No (valid) plugins were selected for ' . operation
     return
   endif
 

autoload/vundle/scripts.vim

@@ -235,14 +235,14 @@ func! s:fetch_scripts(to)
       let cmd = vundle#installer#shellesc(cmd)
     end
   else
-    echoerr 'Error curl or wget is not available!'
+    echoerr 'Vundle error: Neither curl nor wget are available!'
     return 1
   endif
 
   call system(cmd)
 
   if (0 != v:shell_error)
-    echoerr 'Error fetching scripts!'
+    echoerr 'Vundle error: Could not fetch vim-scripts list for searching'
     return v:shell_error
   endif
   return 0