By setting `__bp_delay_install`, we avoid any immediate initialization at all. We then override two troublesome functions before calling `__bp_install_after_session_init()`.
The `__bp_install_after_session_init()` function doesn't enable the DEBUG trap, just sets `$PROMPT_COMMAND` to include `__bp_install()`, so the actual final `$PROMPT_COMMAND` is not finished, and DEBUG trap set, until after the first prompt is displayed.
Added a vendored lib loading routine in bash-it.sh
Added documentation on how to vendor libs in bash-it
Added and fixed plugins using preexec
Added tests for two plugins
Removed the old preexec lib