Consider block parameter for DuplicateMethodCall

This catches cases like the following:

    foo {|a| a.bar}
    foo {|a| a.bar}

In addition, the following cases become extra smelly since the whole
iterator is considered smelly, in additon to `foo.bar`:

    foo.bar {|a| a.baz}
    foo.bar {|a| a.baz}

One consideration is whether the following case should still be
considered smelly:

    foo.bar {|a| a.baz}
    foo.bar {|a| a.qux}

With the present change, this case stays smelly as it was before.
Merge pull request #274 from troessner/duplicate-block-method-call

Consider block parameter for DuplicateMethodCall