rand_chars() returns string in scalar context and tweaked Changes

Hi,

Here's the change to make rand_chars() return a string when called in scalar context:

  * added tests for scalar version for all tests in t/rand_chars.t
  * updated doc

I also tweaked the Changes file, as per my [quest](http://questhub.io/realm/perl/quest/51f0337718ba7d3959000086).
This was mainly changing all dates to ISO 8601 date format, but I also got rid of all tab characters.

BTW, the `jsonmeta` line in Makefile.PL caused `perl Makefile.PL` to barf for me. I just commented it out while testing my changes, as I'm not at all familiar with `Module::Install`.

Cheers,
Neil