Fixed PEAR E_STRICT.

If you are using SMTP, error_reporting for E_STRICT is disabled.
Added a mocking sender for testing applications.
Improved documentation for PEAR senders.
Options for sender are optional and defaulted to an empty array.
Adds profiling support.
Fixes duplicated headers Content-Type in Mail_Sender_Mail.
Sending mail does not alter the sender so it can be reused.