Make resend timeout configurable

Closes #11

See merge request !51

Fix conversion of boolean cli options

See merge request !50

This gives up duck typing but improves error messages.

Expoce functions to get/send stream metadata

See merge request !49

Implement seedee lib for serialisation

See merge request !48

Handle AsapoDataNotInCacheError in AsapoReceiver

Closes #10

See merge request !45

Add retrieve_data method to receiver

See merge request !44

Fix signal handling

See merge request !47

In case the data is not in the cache any more, the data is lost, and
thus a MissingDataError is raised for an AsapoDataNotInCacheError.

SimpleAsapoReceiver can now also throw a MissingDataError, but this
should be ok as a worker either expects this error or it falls back to
the defaul no-op handler.

In case of an AsapoNoDataError, the lastread marker should be advanced.
The AsapoReceiver classes handle this case already correctly.

In case of an AsapoInterruptedTransactionError that advances the
lastread marker, indices were wrongly initialized with 0 instead of 1.

When the environment variable is not set, a library used by ASAPO
installs a signal handler that immediately exits, preventing a graceful
shutdown.

Support ASAPO TV

See merge request !42

Allow mixing Config and attr.ib parameters

See merge request !46

There doesn't seem to be an obvious use case for setting the pipeline
step explicitly. Therefore, removing the option improves the usability.

When Config and attr.ib parameters are mixed and an attr.ib has neither
a type nor a description, the docstring looks better with this change.

This is useful to allow "hidden" parameters that can be used in the
constructor, but are not exposed as options on the command line
or in the configuration file.

Fix StopIteration error on Python >= 3.7

See merge request !41

Bump version v0.0.4

See merge request !40

Do not call converters twice

See merge request !38

Fix configuration with values considered as False

See merge request !37

If a config option uses a converter, it should not be called during
command line parsing because it is already called during construction by
attr.