Refactor project, bump 2.0.0

[hansemannn]

Ok, so what did I do:

• [x] Refactor the code structure to validate properties more clear
• [x] Ensure compatibility with Titanium SDK 5.5.1+
• [x] Add new properties attachments and subject
• [x] Deprecate isSupported and introduce canSendText, canSendSubject and canSendAttachments
• [x] Updated the example