title: What is the difference between ~> and >= when specifying rubygem in Gemfile?
body: <p>I often see the following notation(~>) in Gemfile.</p>
  
  <pre><code>gem "cucumber", "~&gt;0.8.5"
  gem "rspec", "~&gt;1.3.0"
  </code></pre>
  
  <p>I know the sign (>=) is just greater or equal to, but what does the (~>) notation mean?
  Are they both same or has any significant difference?</p>