Make install script unnecessary.

Simplifying bash-it to only need to be sourced with new init script, so
.bash_profile doesn't need to be replaced with a template that is very
bash-it specific. I have a bash_profile with things I like and don't
like it to be messed with much. With the init script, you just need to
source it and bash-it will be loaded.

The install script created the enabled directories when ran. To remove
the install script these directories are created and all content is
ignored.

Removed old backward-compatibilty code from bash-it.

Moved for ; do to a single line. Easier to read.

Remove ignore for aliases/custom.alias.bash and
plugins/custom.plugins.bash. Custom thing should be put in the custom
directory and not spread out over the project.
Surpress any error warnings the Node plugin may display.

Node plugin is looking for npm. On some systems, this will fail silently
and others will print an error message. Surpress error messages on all
systems by piping to /dev/null.
Updated README for this fork.
Removed deprecated plugin z.
Removed old install and init files.