fixed indentation of evil-open-below and evil-open-above in coffee-mode

This is to fix incorrect indentation of a newline after calling `evil-open-below` and `evil-open-above` functions, which are bound to `o` and `O`, respectively.  

Currently, both functions only add one `coffee-tab-width` from beginning of a new line. With this fix, new line is indented according to previous non-empty line.

To clarify what I mean, see below example. `|` indicates cursor position.
```coffee-mode
if true:
  if true:
    if |true:
```
Currently if I hit `o` in normal state, cursor will position at:
```coffee-mode
if true:
  if true:
    if true:
  |
```

With this fix, cursor will position at:
```coffee-mode
if true:
  if true:
    if true:
      |
```
This is also consistent with `coffee-newline-and-indent` function.