Decide on tab settings to be included in ftplugin/fmcalc.vim

[chivalry]

Matt has suggested having the following settings for this plugin:

set tabstop=4
set shiftwidth=4
set noexpandtab
set autoindent

These would seem to be user preferences. If we place them in the plugin files that would override the user's preference in .vimrc and they would have to override our override in ~/.vim/after/plugin/fmcalc.vim.