Add rbfu support.

Prompts can now display the currently active Ruby version set by rbfu, a tool similar to RVM and rbenv.

themes/base.theme.bash

@@ -27,6 +27,9 @@ VIRTUALENV_THEME_PROMPT_SUFFIX='|'
 RBENV_THEME_PROMPT_PREFIX=' |'
 RBENV_THEME_PROMPT_SUFFIX='|'
 
+RBFU_THEME_PROMPT_PREFIX=' |'
+RBFU_THEME_PROMPT_SUFFIX='|'
+
 function scm {
   if [[ -d .git ]]; then SCM=$SCM_GIT
   elif [[ -n "$(git symbolic-ref HEAD 2> /dev/null)" ]]; then SCM=$SCM_GIT
@@ -123,6 +126,12 @@ function rbenv_version_prompt {
   fi
 }
 
+function rbfu_version_prompt {
+  if [[ $RBFU_RUBY_VERSION ]]; then
+    echo -e "${RBFU_THEME_PROMPT_PREFIX}${RBFU_RUBY_VERSION}${RBFU_THEME_PROMPT_SUFFIX}"
+  fi
+}
+
 function virtualenv_prompt {
   if which virtualenv &> /dev/null; then
     virtualenv=$([ ! -z "$VIRTUAL_ENV" ] && echo "`basename $VIRTUAL_ENV`") || return