Replaced '#' for shell command to ';'.

Reference
http://julia.readthedocs.org/en/latest/manual/interacting-with-julia/

Currently, says use '#', which does nothing at the julia> prompt.

Also added a line about using the backspace key, to parallel the same line discussing help mode.
lluang commit added.
Merge branch 'lluang-master'

* lluang-master:
  Replaced '#' for shell command to ';'.