Add zsh configuration files

Since I've switched to zsh, I updated my dotfiles in order to support
zsh. My dotfiles project now supports bash & zsh configuration files.
For zsh configuration files oh-my-zsh framework is used.

The project directory structure has been refactored. Now configuration
files are located inside home/.bash-configs or home/.zsh-configs.

Signed-off-by: Jorge Ramírez <jorgeramirez1990@gmail.com>