Conditionally load completion scripts

bash/completions

@@ -1,5 +1,13 @@
-source ~/.bash/completion_scripts/git_completion
-source `brew --prefix`/Library/Contributions/brew_bash_completion.sh
 complete -C ~/.bash/completion_scripts/rake_completion -o default rake
 complete -C ~/.bash/completion_scripts/project_completion -o default c
 complete -C ~/.bash/completion_scripts/capistrano_completion -o default cap
+
+if which git &> /dev/null; then
+  source ~/.bash/completion_scripts/git_completion
+else
+  echo "Hmmm... git doesn't seem to be installed."
+fi
+
+if which brew &> /dev/null; then
+  source `brew --prefix`/Library/Contributions/brew_bash_completion.sh
+fi