Add checks before loading recent vim features

My env runs on a couple of systems that are so old, fairly recent
vintage vim features are not present. This results in a graceful but
annoying warning I'd rather be rid of. So I've flanked the three main
issue items in version or feature checks.

.vimrc

@@ -8,8 +8,12 @@ call vundle#begin()
 
 " Plugin execution
 Plugin 'VundleVim/Vundle.vim'
-Plugin 'vim-pandoc/vim-pandoc'
-Plugin 'vim-pandoc/vim-pandoc-syntax'
+
+if v:version >= 704
+    Plugin 'vim-pandoc/vim-pandoc'
+    Plugin 'vim-pandoc/vim-pandoc-syntax'
+endif
+
 Plugin 'tpope/vim-surround'
 Plugin 'mhinz/vim-startify'
 Plugin 'vim-airline/vim-airline'
@@ -26,7 +30,9 @@ filetype plugin indent on
 let g:ale_python_pylint_executable = "pylint3"
 
 " Visual themeing
-set termguicolors                 "Enable 256 colors
+if exists('+termguicolors')
+    set termguicolors                 "Enable 256 colors
+endif
 set scrolloff=5                   "Always display 5 lines below cursor when scrolling
 colorscheme hemisu
 set background=dark
@@ -42,7 +48,9 @@ set ignorecase
 set smartcase
 
 " Tabs and Whitespace
-set breakindent
+if exists('+breakindent')
+    set breakindent
+endif
 set autoindent
 set smartindent
 set nowrap