Variable type mismatch in spacevim#bootstrap
I installed a fresh version of Spacevim on Ubuntu 14.04 ("Trusty") using the "Distribution mode" shell line in the readme.

The following error messages are printed when starting vim:

```
Error detected while processing function spacevim#bootstrap:
line  103:
E706: Variable type mismatch for: additional_plugin
Error detected while processing /home/ubuntu/.vimrc:
line   63:
E185: Cannot find color scheme 'gruvbox'
Press ENTER or type command to continue
```

For convenience, here are the relevant lines of `spacevim.vim`, starting at line 103:

```
    if exists('g:dotspacevim_additional_plugins')
      for additional_plugin in g:dotspacevim_additional_plugins
        if type(additional_plugin) == type({})
          Plug additional_plugin.name, additional_plugin.option
        else
          Plug additional_plugin
        endif
      endfor
    endif
```

I take it the second error printed results from the failure to load gruvbox as an additional plugin.

[.vimrc included](https://github.com/ctjhoa/spacevim/files/722142/vimrc.txt)