Moved python test and sjcl to benchmark
Added duration logging to the generate function
Moved XOR into the pbkdf2 class to enable switching logging on/off for
it
'Fixed' test with null character by replacing '\0' with '\u{0000}'. This
is not how I would prefer to do this but I need to research a better way
to do the replacement.

Closes #1
Added support for processing null values in input strings

Closes #1

v0.2.1