[MISC]: Amended TODO
[BUGFIX]: report_error() is only needed if DEBUG is defined
[CLEANUP]: Removed useless char *pwd from shell_t
[FEATURE]: Begin migration to libtecla (http://www.astro.caltech.edu/~mcs/tecla/index.html) partly because of the licensing (MIT just like this shell) and because readline and gnu in general is bad and memory-leaky and bad. Added trivial strip_newline() to shell.c