More hygiene in installer:

* change uninstall.sh to run under zsh, so we have access to better
  file globbing, string substitution, and $ZDOTDIR
* remove additional oh-my-zsh data files in uninstall
* remove unneeded `source ~/.zshrc` in uninstall
* remove bogus `. ~/.zshrc` at end of install.sh: it would just read it
   in the `sh` process running install.sh right before exiting, so it
   would have no effect aside from sometimes kicking out syntax errors.

tools/uninstall.sh

@@ -1,28 +0,0 @@
-echo "Removing ~/.oh-my-zsh"
-if [[ -d ~/.oh-my-zsh ]]
-then
-  rm -rf ~/.oh-my-zsh
-fi
-
-echo "Looking for original zsh config..."
-if [ -f ~/.zshrc.pre-oh-my-zsh ] || [ -h ~/.zshrc.pre-oh-my-zsh ]
-then
-  echo "Found ~/.zshrc.pre-oh-my-zsh -- Restoring to ~/.zshrc";
-
-  if [ -f ~/.zshrc ] || [ -h ~/.zshrc ]
-  then
-    ZSHRC_SAVE=".zshrc.omz-uninstalled-`date +%Y%m%d%H%M%S`";
-    echo "Found ~/.zshrc -- Renaming to ~/${ZSHRC_SAVE}";
-    mv ~/.zshrc ~/${ZSHRC_SAVE};
-  fi
-
-  mv ~/.zshrc.pre-oh-my-zsh ~/.zshrc;
-
-  source ~/.zshrc;
-else
-  echo "Switching back to bash"
-  chsh -s /bin/bash
-  source /etc/profile
-fi
-
-echo "Thanks for trying out Oh My Zsh. It's been uninstalled."