Move `grunt` and `gulp` to separate completion definitions wrapping
`grunt --completion=zsh` and `gulp --completion=zsh` respectively.
Since the completions are loaded lazily on demand, they avoid the
performance overhead during Zsh initialization.
Additionally, remove `npm` completion since it is already bundled with
Zsh for quite a while.
Changes:
- nodenv and nvm now honors (and prioritizes) `$XDG_CONFIG_HOME` over
`$HOME` to lookup local nodenv/nvm installation.
- Make `nvm` loading lazy (via `--no-use` argument).
- Remove redundant NODENV_ROOT or NVM_DIR, respective script already
set them up.
- Adhere to more idiomatic Zsh operation and minimize external command
usage (like `sed`).
This is done to make it easier to not show node-info in themes
when no node version is currently in use. This is consistent with
how the Python module's python-info works.
Signed-off-by: Sorin Ionescu <sorin.ionescu@gmail.com>
