Suggested specs for call nodes, including the tricky new unary call node.
Left dummy spec in by mistake.
Merge branch 'master' into issue-8-proposed-specs
New class, UnaryClassNode, to express the subtletly of calls to the -, + and -@, +@ methods.
Remove possible failing specs for not operator.
Merge pull request #22 from chrisseaton/issue-8-proposed-implementation

Fixes #4.
Simplify UnaryCallNode - it doesn't need arguments - and implement it for ReWriteVisitor.
getDecoratedName → getLexicalName
New specs for 'not' and '!' with use of lexical name when 'not'.
Tidy up 'not' and '!' specs.