This commit removes a check I added when working on number input
issues where we perform a loose check on an input's value before we
assign it. This prevented controlled text inputs from disallowing
numeric text entry.

I also added a DOM fixture text case.

Related issues:

facebook#9561 (comment)

This commit adds back the guard around assigning the value property to
an input, however it does it using a strict equals. This prevents
validated inputs, like emails and urls from losing the cursor
position.

It also adds associated test fixtures.