Conversations support (beta)
IMP Added References header support

In case wich In-Reply-To is insuficient we try to search with
References header.
FIX typo
IMP notificar poweremail
Not send duplicate emails
Check if no email is given
Merge pull request #11 from gisce/no_dup_to

Not send duplicate emails
Bump to v0.8.0
IMP vincular el src_id
IMP treure el poweremail del context
Merge pull request #12 from gisce/callbacks

Callbacks
Bump to v0.9.0
Merge branch 'conversations' into v5_backport
Bump to v0.10.0