add isAPowerOfTwo
added JavaDoc and tests for BasicMath::gcd
fixed BigInteger generation, added some tests
enforce non-removability of Iterators
added JavaDoc and tests for random negative numbers
added JavaDoc and tests for random natural numbers
added JavaDoc and tests for remaining random numbers
improved random number generation, added chars
added JavaDoc and tests for characters
added tests for random floats and doubles
added and tested exhaustive BigDecimal generators
add and test geometrically distributed integers
added random BigDecimalIterables