title: NSDecimalNumber doubleValue incorrect for digit 7
body: <p>How can I store '0.07' value except NSDecimalNumber? I mean I can't using NSDecimalNumber because when I'm using <code>doubleValue</code> function, <code>decimal 0.07</code> becomes <code>0.0699999... double</code> or something else, but never <code>0.07 double</code> :) </p>
  
  <p>Example from debugger:</p>
  
  <pre><code>(lldb) po [[NSDecimalNumber alloc] initWithDouble:.07]
  0.07000000000000001024
  
  (lldb) po [[NSDecimalNumber alloc] initWithDouble:(double).07]
  0.07000000000000001024
  
  (lldb) po [[[[NSDecimalNumber alloc] initWithDouble:7] decimalNumberByDividingBy:[[NSDecimalNumber alloc] initWithDouble:100]] doubleValue]
  0.069999999999999993
  
  (lldb) po 0.07
  0.070000000000000007
  
  (lldb) po (double)0.07
  0.070000000000000007
  </code></pre>
  
  <p>The only way to store 0.07 is NSDecimalNumber, but it's inconvenient:</p>
  
  <pre><code>(lldb) po [[[NSDecimalNumber alloc] initWithDouble:7] decimalNumberByDividingBy:[[NSDecimalNumber alloc] initWithDouble:100]]
  0.07
  </code></pre>