add thesaurus (see below for steps)

installation instructions:

    - Download thesaurus: http://www.gutenberg.org/dirs/etext02/mthes10.zip
    - unzip mthes10.zip
    - mkdir ~/.vim/thesaurus
    - cp mthesaur.txt ~/.vim/thesaurus/

add to .vimrc:

    set thesaurus+=~/.vim/thesaurus/mthesaur.txt

usage:

    <C-X><C-T>