MacOS – rbenv global version of ruby vs Sierra ruby version

Following this OSX Sierra tutorial from the folks at gorails, I am having trouble getting rbenv global to associate the install of 2.3.0 with the ruby command and to override the default ruby version on my MacBook Air with macOS Sierra v10.12.2

$  rbenv -v
rbenv 1.1.0
$  rbenv install 2.3.0
/Users/user_name/.rbenv/versions/2.3.0 installed
$  rbenv global 2.3.0
$  ruby -v
ruby 2.0.0p648 (2015-12-16 revision 53162) [universal.x86_64-darwin16]

I tried rbenv rehash but ruby2.0.0 is still the default version. Briefly reviewing this blog about ruby and $PATH environment, I find I'm a little lost as to where the default Ruby "executable" actually lives…

gem env shows me that Ruby 2.0.0 lives here:

/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby

and whereis tells me something different:

$  whereis ruby
/usr/bin/ruby

The tutorial says to add rbenv to my .bash_profile

echo 'if which rbenv > /dev/null; then eval "$(rbenv init -)"; fi' >> ~/.bash_profile source ~/.bash_profile`

Do I need to set my path to ignore the default ruby?

For what it is worth:

$  rbenv exec ruby -v
ruby 2.3.0p0 (2015-12-25 revision 53290) [x86_64-darwin16]

but obviously I don't want to write out the executive command everytime I want to use ruby… Per the blog, adding eval "$(rbenv init -)" doesn't make the ruby command defer to the rbenv global version… Help.