node, python, ruby: update docs about new envars

modules/node/README.md

@@ -10,6 +10,9 @@ nvm
 [nvm][5] allows for managing multiple, isolated Node.js installations in the
 home directory.
 
+This will be loaded automatically if nvm is installed in `$NVM_DIR`,
+`~/.nvm`, or nvm is installed with homebrew.
+
 nodenv
 ------
 
@@ -17,6 +20,9 @@ nodenv
 Node versions. It's simple and predictable, Just Works, and is rock solid in
 production. nodenv is forked from the popular [rbenv][7].
 
+This will be loaded automatically if nodenv is installed in `$NODENV_ROOT`,
+`~/.nodenv`, or `nodenv` is on the path.
+
 Functions
 ---------
 

modules/python/README.md

@@ -35,6 +35,9 @@ execution of `pyenv`.
 
 Install Python versions with `pyenv install` into `~/.pyenv/versions`.
 
+This will be loaded automatically if pyenv is installed to `$PYENV_ROOT`,
+`~/.pyenv`, or if the `pyenv` command is on the path.
+
 Local Package Installation
 --------------------------
 

modules/ruby/README.md

@@ -32,6 +32,9 @@ multiple, isolated Ruby installations in the home directory.
 While it is not as feature rich as RVM, it is not loaded into the shell and is
 not known to cause conflicts with shell scripts.
 
+This will be loaded automatically if rbenv is installed to `$RBENV_ROOT`,
+`~/.rbenv`, or if the `rbenv` command is on the path.
+
 chruby
 ------