Failing spec for #19.
Fixes #19, but only when the colon is explicit.
Merge pull request #20 from chrisseaton/github-issue-19

Fixes GH #19
Suggested specs for call nodes, including the tricky new unary call node.
Left dummy spec in by mistake.
Apart from some of the call position specs, all specs pass with 2.0 as well, so switch to using VERSIONS constant.
Fixes #21.
Update and tidy README.
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.
Add default for being able to just type 'mvn'...yes
Add missing method to noopvisitor
Update to next version
SequenceMatcher better able to handle moved code

This is a big improvement, but I've only just realized
that a part of my approach has been wrongheaded. I need
a way to measure the distance between two nodes, and
can probably discard these ideas about complexity and
depth. A simple levenshtein distance taken on the raw
strings may be enough, or I may have to come up with
some measurement specific to an AST.