Generator for simple sequence diagrams

Format example

// Lines that do not start with @ and does not contain "arrow" ignored
// and can be used as comment

// Actor is declared in format @<identifier> <optional full name>
// Identifier must not contain spaces
@alice Alice
@bob Bob
@eva Eva

// Message is declared as <sender> -> <receiver> <optional message description>  
// or <receiver> <- <sender> <optional message description>
alice -> bob Message