Introduce T for opening files in tabs

Closes #39.

autoload/startify.vim

@@ -82,6 +82,7 @@ function! startify#insane_in_the_membrane() abort
   nnoremap <buffer><silent> i             :enew <bar> startinsert<cr>
   nnoremap <buffer><silent> b             :call <sid>set_mark('B')<cr>
   nnoremap <buffer><silent> s             :call <sid>set_mark('S')<cr>
+  nnoremap <buffer><silent> t             :call <sid>set_mark('T')<cr>
   nnoremap <buffer><silent> v             :call <sid>set_mark('V')<cr>
   nnoremap <buffer>         <cr>          :call <sid>open_buffers(expand('<cword>'))<cr>
   nnoremap <buffer>         <2-LeftMouse> :execute 'normal' matchstr(getline('.'), '\w\+')<cr>
@@ -370,7 +371,7 @@ function! s:set_mark(type) abort
   setlocal modifiable
 
   " set markers
-  if id =~# '[BSV]'
+  if id =~# '[BSTV]'
     " replace marker by old ID
     execute 'normal! ci]'. remove(s:marked, line('.'))[0]
   else
@@ -406,6 +407,13 @@ function! s:open_buffers(cword) abort
         else
           execute 'vsplit' path
         endif
+      " open in tab
+      elseif type == 'T'
+        if line2byte('$') == -1
+          execute 'edit' path
+        else
+          execute 'tabnew' path
+        endif
       " open in current window
       else
         execute 'edit' path

doc/startify.txt

@@ -53,10 +53,10 @@ Startify basically provides two things:
    jumps into insert mode, 'q' quits.
 
    Moreover, you can open several files at one go. Navigate to an entry and
-   hit either 'b' (open in same window), 's' (open in split) or 'v' (open in
-   vertical split). You can do that for multiple entries. You can also mix
-   them. The order of the selections will be remembered. Afterwards execute
-   these actions via <cr>.
+   hit either 'b' (open in same window), 's' (open in split), 'v' (open in
+   vertical split) or 't' (open in tab). You can do that for multiple entries.
+   You can also mix them. The order of the selections will be remembered.
+   Afterwards execute these actions via <cr>.
 
    When the selection is finished, Startify will close automatically. You can
    reopen the screen via :Startify.
@@ -261,7 +261,7 @@ NOTE: There is no sanitizing going on, so you should know what you're doing!
 Best practices:
 
 - do not use 'e', 'i' or 'q'  (they will be overwritten anyway)
-- do not use 'b', 's', 'v'  (used for opening several files at once)
+- do not use 'b', 's', 't', 'v'  (used for opening several files at once)
 - do not use duplicates  (previous mappings will be overwritten)
 - do not uses empty strings  (creates unreachable entries)
 - you might want to keep 'j' and 'k'  (for navigation)