Remove '..' alias.

- cd ..; cd ../..; cd ../../..; cd ../../../.. are aliased by
  default on zsh to ..; ...; ....; ..... respectively.
Use vim instead of vi.

- vi command uses vim that comes with the system instead of the one of MacVim.
Delete yuv alias, as asked by the comment.
Merge pull request #237 from rafaelregis/aliases_cleanup

Aliases cleanup