title: Compilation Error with NSParameterAssert with Xcode 6.3
body: <p>I am getting compilation errors anywhere NSParameterAssert is used. For example:  </p>
  
  <pre><code>-(instancetype)initForPlot:(CPTPlot *)plot withFunction:(CPTDataSourceFunction)function
  {
      NSParameterAssert([plot isKindOfClass:[CPTScatterPlot class]]);
      NSParameterAssert(function);
  
      if ( (self = [self initForPlot:plot]) ) {
          dataSourceFunction = function;
      }
      return self;
  }
  </code></pre>
  
  <p>The code compiles fine with Xcode 6.2 but it's giving me the following errors with Xcode 6.3:<br>
  <code>/Users/xxxx/Project/App/Presentation/CorePlot/Source/CPTFunctionDataSource.m:110:5: Using %s directive in NSString which is being passed as a formatting argument to the formatting method</code>  </p>
  
  <p>I have looked up online and have not seen information on the error message.<br>
  A temp fix I am using is the following:  </p>
  
  <pre><code>#undef NSParameterAssert
  #define NSParameterAssert(condition)    ({\
  do {\
  _Pragma("clang diagnostic push")\
  _Pragma("clang diagnostic ignored \"-Wcstring-format-directive\"")\
  NSAssert((condition), @"Invalid parameter not satisfying: %s", #condition);\
  _Pragma("clang diagnostic pop")\
  } while(0);\
  })
  </code></pre>
  
  <p>There should be a better solution for this though.  </p>