Fix compatibility with xonsh

vimrc

@@ -27,6 +27,7 @@ set foldopen-=search " do not open folds if there's a match inside them
 set cursorline " highglight the line on which the cursor is atm.
 set lazyredraw " redraw screen only when macro has finished, increases execution speed
 set nojoinspaces " don't produce two spaces on 'J' when a line ends with a period
+set shell=/bin/bash " to be compatible with xonsh
 set autochdir " automatically set working directory to path of open file.
 " actually cd to the current file (the above is only applied upon changing file)
 cd %:p:h