Bug/reader

[seanpearsonuk]

• skip bad scheme input in lispy.py: `(define "string not symbol")'. Before this change, it raises an exception, aborting the whole read. The read can still be salvaged.
• allow e.g. (define x). Before this change, only e.g. (define x value) is possible
• make input parameter search more flexible in case reader
• add some lispy tests relevant to the above
• extended case reader testing with the case from the issue.N.b. before the lispy changes, the read raises an exception; before the reader changes, the input parameters are empty. N.b. the case contains gobbledygook.

#788 is fixed with this.