Unknown function: vundle#begin

Your .vimrc seems fine. Looks like you have not installed the vundle plugin properly. Run this command on your console.

git clone https://github.com/gmarik/Vundle.vim.git ~/.vim/bundle/Vundle.vim

You should have a directory structure like (I simplified it):

~/.vim
├── bundle/
│   └── Vundle.vim  <------------------ Vundle
├── colors/
│   └── Tomorrow.vim
└── plugin/
    └── acp.vim

maybe the rtp location is wrong,you can type

:echo &rtp  

in Vim to see whether the location of ~ stand for is correct.

you can replace

set rtp+=~/.vim/bundle/Vundle.vim

to

set rtp+=/home/[YourUserName]/.vim/bundle/Vundle.vim   //do not use ~