select options, some backwards incompatibilities.

I couldn't find a nice way to select an <option> from a dropdown, so I wrote it.

We were using find("#myselect option[value=3]").click() but this appears to cause some strange issues in firefox, perhaps due to recent changes in selenium.

Seems the correct way to do it is via http://selenium.googlecode.com/svn-history/r15117/trunk/docs/api/rb/Selenium/WebDriver/Support/Select.html

In adding support for this to WebElement, I found that webdriver calls WebElement.is_selected(), but that throws an error because for some reason it's a property in webdriverplus. To fix that I changed it (and the other is_* properties) back to methods. I agree properties are nicer but it's prohibitive to not be able to use normal webdriver APIs with the WDP WebElement.

I don't think there's a sane way to change properties back to methods in a backwards-compatible way, unfortunately. I suppose technically you could subclass `boolean` and add a `__call__` method. Let's not do that.