Fix Bash implementation interop carriage returns.

[chr15m]

Before this fix the 'sh*' function was joining the lines of the output of whatever command was run in a way that resulted in '\n' instead of a literal carriage return.

Without this fix:

$ ./mal
Mal [bash]
user> (println (sh* "head mal"))
#!/usr/bin/env bash\n#\n# mal (Make a Lisp) object types\n#\n\nif [ -z "${__mal_types_included__}" ]; then\n__mal_types_included=true\n\ndeclare -A ANON\n
nil

After this fix (carriage returns correctly inserted by sh*):

$ ./mal
Mal [bash]
user> (println (sh* "head mal"))
#!/usr/bin/env bash
#
# mal (Make a Lisp) object types
#

if [ -z "${__mal_types_included__}" ]; then
__mal_types_included=true

declare -A ANON


nil

[chr15m]

Added more tests, fixed the stripping of the final \n, and allow sh* to capture output which has no \n at all within it.