0_path.zsh reinserts .yadr paths twice in tmux

in terminal
```sh
sky@nimbus ~ $ echo $PATH 
/Users/sky/.rbenv/shims:/Users/sky/.rbenv/bin:/usr/local/bin:/usr/local/sbin:/usr/bin:/bin:/usr/sbin:/sbin:/usr/X11/bin:/Users/sky/.yadr/bin:/Users/sky/.yadr/bin/yadr
```

in tmux

```sh
sky@nimbus ~ $ echo $PATH
/Users/sky/.rbenv/bin:/usr/local/bin:/usr/local/sbin:/usr/bin:/bin:/usr/sbin:/sbin:/usr/X11/bin:/Users/sky/.rbenv/shims:/Users/sky/.yadr/bin:/Users/sky/.yadr/bin/yadr:/Users/sky/.yadr/bin:/Users/sky/.yadr/bin/yadr
```
Update docs
If you don't use a solarized terminal, you have to set g:yadr_using_unsolarized_terminal now [Ref #487]
Explain how to deal with unsolarized terminals in docs
Add the agnoster prompt, with customizations
Merge pull request #497 from Sumukh/master

Added the Agnoster prompt as an option.
Merge pull request #506 from padi/patch-1

0_path.zsh reinserts .yadr directories twice in $PATH when in tmux