code clean up

Author: plokhotnyuk

src/main/java/com/jsoniter/IterImplNumber.java

@@ -62,8 +62,7 @@ class IterImplNumber {
  }
 
  public static final double readDouble(final JsonIterator iter) throws IOException {
- final byte c = IterImpl.nextToken(iter);
- boolean negative = c == '-';
+ boolean negative = IterImpl.nextToken(iter) == '-';
  if (!negative) {
  iter.unreadByte();
  }