Remove swiftmailer dependency.
Merge branch 'master' into develop
Add missing support for $offset and $limit in csv recipient source.
Merge branch 'release/1.0.1'
Merge tag '1.0.1' into develop

Version 1.0.1
Add null transport implementation.
Merge branch 'release/1.1'
Merge tag '1.1' into develop

Version 1.1
Replace illegal ~X constraints with ~X.Y constraints.
Merge branch 'release/1.1.1'
Merge tag '1.1.1' into develop

Version 1.1.1
Bugfix, use arrays in array_merge.
Merge branch 'release/1.1.2'
Merge tag '1.1.2' into develop

Version 1.1.2
Fix offset+limit issue give lines twices.

If there is an invalid row between two lines, the current offset+limit
logic will return some lines twice or completely skip lines. Now it
works by using a separate $index variable to determine the passed lines,
but the method may return less than $limit recipients.
Use swift grammar to validate email addresses in csv file.
Write a unit test for csv file recipient source.
Merge branch 'release/1.1.3'
Merge tag '1.1.3' into develop

Version 1.1.3
Refactore CSVFile::getRecipient() will not return all recipients

When using CSVFile::countRecipients() is used to determine the maximum
$offset+$limit value, you may not receive all recipients with the old
logic.