Remove vim-shell

This plugin causes random hanged vim.exe and cmd.exe processes on
Windows.  I had several dozen after working in Vim all day.
Support bash shell on Windows
Fix easytags errors when using bash on Windows

Easytags was running the ctags --version command after bash was set as
shell, but before Vim had set all the automatic configurations needed to
make bash work in Windows Vim.  This sets the automatic configurations
in vimrc.
Readme tweaks