Cant customize the input control.

### I'm Submitting a ...

```
[ ] Bug report
[ ] Feature request
[x] Support request
```

### Steps to Reproduce
Im on react-datetime v 2.16.3 and am trying to resize the input text box but have not been successful. Thigs I tried include adding inline style for font size and hieght. Adding a new .css file and adding the class in in the className prop

### Expected Results
I was hoping for the text box to shrink

### Actual Results
The style from the css is applied to the text in the date time picker.