Bug fix: zstyle name typo; missing prefix for sourcing hooks

Hi Valodim, I fixed some minor bugs in the scripts:
1. for the zstyle commands, some "powerline" are mistyped as "poweline"; and a trailing ':' is missing from some of them
2. when example_config.zsh is sourced from a script in another dir e.g. ~/.zshrc, the paths for hooks need to be prefixed by the parent dir of the config.zsh file