md-input-container should ignore hidden fields as part of the inputs its counting.

[heavysixer]

I understand the purpose of having only a single visible input per container but this should not apply to hidden fields. Hidden fields are often used to track default parameters and therefore should be logically organized near the visible input. Consider the following example:

<md-input-container class="md-default-theme">
      <input name="account[remember_me]" type="hidden" value="0" class="md-input" id="input_001">
      <input type="checkbox" value="1" name="account[remember_me]" id="account_remember_me">
      <label for="account_remember_me">Remember me</label>
</md-input-container>