[BUG-FIX]: extra new line

In some cases the `buffer` may exceed the allowed `width`. When this
happens, the closing tag may still be in the buffer and it just may
happen that the place where the `buffer` will be cut is at the end of
the closing tag. This makes the writer print the new line character.
Now we are at a position in which we need to decide if we want to print
another new line. We wish to do this only if the node is a `BLOCK` node
(but with the extra condition added to the code). The `li` element has
also been added to the `BLOCK` list.
[NEW]: add and delete from BLOCK

This writing style has several elements that are treated as blocks.
That is, we display them in a separate line. Sometimes however, you may
wish to have some other elements treated as blocks, or perhaps you
don't wish certain element in the defaults to be treated as a block.
For this reason I have added the options `add_block` and `del_block`.
When using the command line use the form `@add_block=[ele1,ele2]` to
have your elements added to the list, or `@del_block=[ele1,ele2]` to
remove them from it. Note that regardless of the order in which you
specify the options, the `pre_process` function in this style will
first perform the appending of the elements and then the deletion of
the elements.