src/fs.php: Add "makeTempDir" function.
src/array.php: Add 'TODO' comment regarding fact that 'head' function does not leave the given array's "internal pointer" unmolested.
Some substantial work on our email lib, and an enhanced mechanism for testing the email lib as well, whereby messages will be saved to a temporary directory (in raw email format, as passed to the "sendmail" script) allowing test-cases to subsequently locate the messages and make assertions against their content.
src/email.php: Add special check to make sure UTF-8-encoded emails (which is now the default specified in Content-Type header) *are in fact* UTF-8; if not, raise an InvalidArgumentException.