Reads the next object from stream, which must be an instance of
java.io.PushbackReader or some derivee. stream defaults to the
current value of *in*.
Reads data in the edn format (subset of Clojure data):
http://edn-format.org
opts is a map that can include the following keys:
:eof - value to return on end-of-file. When not supplied, eof throws an exception.
:readers - a map of tag symbols to data-reader functions to be considered before default-data-readers.
When not supplied, only the default-data-readers will be used.
:default - A function of two args, that will, if present and no reader is found for a tag,
be called with the tag and the value.