Handle newlines better in URWIDRepl.echo (closes #150).
Handle newlines better in URWIDRepl.echo (closes #150).

We were incorrectly using multiple lines for each call to echo even if
the displayed string did not end in a newline. This fixes it by
reusing the last urwid Text widget in that case, adding an implicit
newline on prompt.

kdart/bpython,kdart/bpython,wevial/bpython,aktorion/bpython,aktorion/bpython,wevial/bpython