yum remove ruby

cd <your-ruby-source-path>
make uninstall

wget ftp://ftp.ruby-lang.org/pub/ruby/2.1/ruby-2.1.7.tar.gz

tar zxvf ruby-2.1.7.tar.gz
./configure --disable-install-rdoc
make
make prefix=/usr/local install

gem sources --remove https://rubygems.org/
gem sources -a https://ruby.taobao.org/
gem sources -l

gem install bundler --no-doc

ln -s /usr/local/bin/ruby /usr/bin/ruby  
ln -s /usr/local/bin/gem /usr/bin/gem  
ln -s /usr/local/bin/bundle /usr/bin/bundle  

[root@test81 ~]# which ruby
#/usr/local/bin/ruby
[root@test81 ~]# which gem
#/usr/local/bin/gem
[root@test81 ~]# which bundle
#/usr/local/bin/bundle
[root@test81 ~]# ruby -v
#ruby 2.1.7p400 (2015-08-18 revision 51632) [x86_64-linux]