Bug fix #2 and validateKeySize() method

There is a bug depend to MCrypt's blowfish ecb algorithm.
mcrypt_enc_get_supported_key_sizes() returns empty array.
mcrypt_enc_get_key_size() works fine. I added condition
to check empty array and use mcrypt_enc_get_key_size()
if array is empty.

Also I added new method validateKeySize(). This method
enables/disables strict key checking on open() method.