DateInput component

[rbx44]

1. DateInput component width on render is not consistent with other components.. I believe it has to do with the class "slds-dropdown-trigger" it is wrapped inside.

2. DateInput doesn't have a default value and that's why it gives react uncontrolled warning. "Warning: A component is changing an uncontrolled input of type undefined to be controlled. "

Please fix these two issues in DateInput.

[rbx44]

Also, when you scroll out the dateInput field on the page, the calendar/dateInput view doesn't go away.

[rbx44]

@stomita Any updates on this?