Add repl prompts

Author: mikeingold

docs/src/tutorial.md

@@ -82,12 +82,12 @@ The alias function `lineintegral` works for this geometry since it has one
 parametric dimension. However, the aliases `surfaceintegral` and `volumeintegral`
 will throw an `ArgumentError` since the geometry is not a surface or volume.
 ```jldoctest tutorial
-lineintegral(f, curve)  # -> Approximately 2π Ω
+julia> lineintegral(f, curve)  # -> Approximately 2π Ω
 
-surfaceintegral(f, curve)  # -> throws ArgumentError
+julia> surfaceintegral(f, curve)  # -> throws ArgumentError
 ERROR: ArgumentError: Performing a surface integral on a geometry with 1 parametric dimensions not supported.
 
-volumeintegral(f, curve)  # -> throws ArgumentError
+julia> volumeintegral(f, curve)  # -> throws ArgumentError
 ERROR: ArgumentError: Performing a volume integral on a geometry with 1 parametric dimensions not supported.
 ```