refactor: clean up vimrc - remove unused gruvbox, autochdir, duplicate syntax

vimrc

@@ -11,7 +11,6 @@ call vundle#begin()
 Plugin 'VundleVim/Vundle.vim'
 
 " Plugins
-Plugin 'morhetz/gruvbox'
 Plugin 'preservim/nerdtree'
 Plugin 'tpope/vim-fugitive'
 Plugin 'tpope/vim-surround'
@@ -43,18 +42,16 @@ set guioptions=
 set showmode
 set showtabline=0
 set smartcase
-set autochdir
 set number
 set ruler
 set wrap linebreak nolist
-set textwidth=80
 set cursorline
+autocmd FileType text,markdown setlocal textwidth=80
 
 " Force 256 color support
 set t_Co=256
 
 " Enable syntax highlighting
-syntax enable
 syntax on
 
 " Set syntax highlight for specified file types
@@ -147,12 +144,14 @@ let g:syntastic_check_on_open = 1
 let g:syntastic_check_on_wq = 0
 
 " Change mode cursor color in xterm
+" Avoid spawning shell (silent !echo) which causes garbage output in some terminals.
+" t_EI is sent on VimEnter automatically when leaving insert mode context.
 if &term =~ "xterm-256color\\|rxvt"
   let &t_SI = "\033]Pl00d7ff\033\\"
   let &t_SR = "\033]Plf00000\033\\"
   let &t_EI = "\033]Plff8708\033\\"
-  silent !echo -ne "\033]Pla0522d\033\\"
-  autocmd VimLeave * silent !echo -ne "\033]Plc1ffc1\033\\"
+  autocmd VimEnter * let &t_EI = "\033]Plff8708\033\\" | redraw
+  autocmd VimLeave * try | call writefile(["\033]Plc1ffc1\033\\"], '/dev/tty') | catch | endtry
 endif
 
 " Show tabs and trails