Better smarparens behaviour for braces

For curly braced languages like C, currently the brace behaviour is very annoying.

Typing this `int main() {` and hitting enter produces:
```c
int main() {
|} // | is the cursor
```
With the changes in this PR typing the same thing and hitting enter produces:
```c
int main() {
    |
}
```

@Wolfy87 I know you use Spacemacs for JS, have you had this problem?