added documentation about how to install Swiftmailer from the PEAR channel
added documentation about how to install Swiftmailer from the PEAR channel

Dubz/swiftmailer,zghosts/swiftmailer,voku/swiftmailer,handautsav/swiftmailer,gencer/swiftmailer,tweakers-dev/swiftmailer,fvosberg/swiftmailer,papagel/swiftmailer,swiftmailer/swiftmailer,Pardot/swiftmailer,deguif/swiftmailer,UofSC/php-shared-functions,kuslahne/swiftmailer,Chhunlong/swiftmailer,denpamusic/swiftmailer,gburyakovsky/swiftmailer,Pardot/swiftmailer,c960657/swiftmailer,UofSC/php-shared-functions,michabbb-backup/swiftmailer,peterkokot/swiftmailer,Dubz/swiftmailer,Rotzbua/swiftmailer,jamesggordon/swiftmailer,peterkokot/swiftmailer,papagel/swiftmailer,handautsav/swiftmailer,robertklein/swiftmailer,tweakers-dev/swiftmailer,swiftmailer/swiftmailer,Pardot/swiftmailer,c960657/swiftmailer,jamesggordon/swiftmailer,gencer/swiftmailer,Pardot/swiftmailer,gburyakovsky/swiftmailer,robertklein/swiftmailer,voku/swiftmailer,zghosts/swiftmailer,kuslahne/swiftmailer,UofSC/php-shared-functions,denpamusic/swiftmailer,Chhunlong/swiftmailer,deguif/swiftmailer,peterkokot/swiftmailer,fvosberg/swiftmailer,michabbb-backup/swiftmailer,Rotzbua/swiftmailer