Dont prefix $PATH with zplug paths, append $PATH instead

[nerd190]

Is your feature request related to a problem? Please describe.
A clear and concise description of what the problem is. Ex. I'm always frustrated when [...]

Describe the solution you'd like
A clear and concise description of what you want to happen.

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.

Hi, thank you for zplug, please do not prefix our path with zplug directories, append the path with zplug directories instead. Thank you again.