Dropping dependency on the imap library

This is a combination of 11 commits.
Eliminating dependency on imap library

Deleting dependency from composer file

Adding PHP5.3 to the battery test and preparing tests for new function

Example file for mimeHeaderDecode function

Better function description

Searched up tests from php source code to add them here as well

Also fixed some minor upper/lower case issues

Some more test cases and plan of action

Excluding some directories from code coverage report

Another simple case

PHPUnit Group annotation fix

All tests pass and ready drop-in replacement