maybe have a test that does..

```java
BitArray.fromValue(longWhereLeastAndMostSigBitAreSet)

 assertTrue(b.get(0))
 assertFalse(b.get(1))
 assertTrue(b.get(63))
 assertFalse(b.get(64))
 b.set(64); // grows when initializedFromLong
 assertFalse(b.get(64))
```