Merge pull request #39 from umop/umop-last_visible_row

added (get)lastVisibleRow to editor.dart and virtual_renderer.dart
ace.proxy : remove usages of `new js.JsFunction.withThis`

In all cases where we were using this ctor we don't need access to the
js 'this' so it was unnecessary overhead; we can simply install dart
closures and `dart:js` should proxy them automatically.
ace_test.html : remove the `interop.js` script

This is no longer needed and including it generates a warning, so I'm
removing it.
add library `ace.test.mocks`
make `HasProxy` a public type so that `MockVirtualRenderer` can extend it

this is necessary so that we can inject it into the `new
Editor(VirtualRenderer, Session)` constructor.  The `EditorProxy` needs
to be able to extract the `jsProxy` from the renderer / session
instances.
MockVirtualRenderer : more progress
MockVirtualRenderer : working implementation
editor_test : add a `mockRenderer` and use it in `testFirstVisibleRow` and `testLastVisibleRow`
Merge pull request #41 from rmsmith/mock_virtual_renderer

Mock virtual renderer
CHANGELOG : add a note for the `lastVisibleRow` getter
LICENSE
pubspec : bump unittest min version
updated to ace-builds 04.11.2014
release version 0.3.7+4.11.2014
0.3.8-dev+4.11.2014
pure/README : update text

now that we have separate library imports for proxy and pure impls this
text about tree-shaking no longer makes any sense.
code completion sample
remove cache directory
_EditSessionProxy : add named optional `listen` to the ctor that defauls to `true`

Allows us to avoid listener creation / attachment for short-lived
proxies such as those passed to a code completer call
js/README : tweak