fix Vagrantfile so that the correct ruby is installed

Prior to this commit, the vagrantfile installs ruby 2.3.3. Due to commit 7951e7ff, this no longer works.

Change the provision scrip so that 2.3.1 is installed via rbenv. Note this drastically increases provision time.

Vagrantfile

@@ -9,9 +9,6 @@ cd /vagrant # This is where the host folder/repo is mounted
 curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | sudo apt-key add -
 sudo apt-add-repository 'deb https://dl.yarnpkg.com/debian/ stable main'
 
-# Add repo for Ruby 2.3 binaries
-sudo apt-add-repository ppa:brightbox/ruby-ng
-
 # Add repo for NodeJS
 curl -sL https://deb.nodesource.com/setup_4.x | sudo bash -
 
@@ -24,31 +21,43 @@ sudo apt-get install iptables-persistent -y
 # Add packages to build and run Mastodon
 sudo apt-get install \
   git-core \
-  ruby-build \
+  g++ \
   libpq-dev \
   libxml2-dev \
   libxslt1-dev \
   imagemagick \
   nodejs \
-  ruby2.3 \
-  ruby2.3-dev \
-  ruby-switch \
   redis-server \
   redis-tools \
   postgresql \
   postgresql-contrib \
   yarn \
+  libreadline-dev \
   -y
 
-# Set Ruby 2.3 as 'ruby'
-sudo ruby-switch --set ruby2.3
+# Install rbenv
+git clone https://github.com/rbenv/rbenv.git ~/.rbenv
+cd ~/.rbenv && src/configure && make -C src
+echo 'export PATH="$HOME/.rbenv/bin:$PATH"' >> ~/.bash_profile
+echo 'eval "$(rbenv init -)"' >> ~/.bash_profile
+
+git clone https://github.com/rbenv/ruby-build.git ~/.rbenv/plugins/ruby-build
+
+export PATH="$HOME/.rbenv/bin::$PATH"
+eval "$(rbenv init -)"
+
+echo "Compiling Ruby 2.3.1: warning, this takes a while!!!"
+rbenv install 2.3.1
+rbenv global 2.3.1
+
+cd /vagrant
 
 # Configure database
 sudo -u postgres createuser -U postgres vagrant -s
 sudo -u postgres createdb -U postgres mastodon_development
 
 # Install gems and node modules
-sudo gem install bundler
+gem install bundler
 bundle install
 yarn install
 
@@ -62,7 +71,6 @@ $start = <<SCRIPT
 
 cd /vagrant
 export $(cat ".env.vagrant" | xargs)
-killall ruby2.3
 rails s -d -b 0.0.0.0
 
 SCRIPT