Right aligns "Use" and "Additional help topics"

If a command was especially long (> 15 char), the right alignment wouldn't work properly. Example:
```
Available Commands:
  views [<db>...]           :: Print all views
  refreshviews [<db>...] [--verbose] :: Refresh all views
````

Same issue with the *Additional help topics* (> 11 char)
```
Additional help topics:
  hugolong version :: Prints the version
  hugolong server :: Print basic server info
```

This commit attempts to properly align regardless of length:
```
Available Commands:
  views [<db>...]                    :: Print all views
  refreshviews [<db>...] [--verbose] :: Refresh all views

Additional help topics:
  hugolong version      :: Prints the version
  hugolong server       :: Print basic server info
```