"--ignore-all-space" invalid

```   
const gitDiff = require('git-diff')
    const oldStr = 'fred\n   is   \nfunny\n'
    const newStr = 'fred\n   is   \nfunny  \n'
    const diff = gitDiff(oldStr, newStr, { flags: '--diff-algorithm=minimal --ignore-all-space' })
```
result：
```
 fred
    is   
-funny
+funny  
```