fix(Parsing): Handle more AST nodes; log don't raise

[nokome]

Currently, there are some AST nodes that are passed (ie. not parsed :) and all others not handled throw TypeError:

pyla/stencila/pyla/code_parsing.py

Lines 271 to 274 in 1359825

	elif isinstance(statement, (ast.ClassDef, ast.Num, ast.Str, ast.Pass)):
	pass
	else:
	raise TypeError('Unrecognized statement: {}'.format(statement))

While trying to compile someipynb files from the wild I got exceptions thrown for:

• NameConstant
• UnaryOp
• Lambda

I think all of these probably need to be handled. Also, I wonder if it would be better to log instead of to raise for unhandled nodes e.g.

        elif isinstance(statement, (ast.ClassDef, ast.Num, ast.Str, ast.Pass)):
            pass
        else:
            LOGGER.warning(...)