fix issue #1007 , email style arrow quote conversion to html error

[bukn]

Steps for submitting a pull request:

• [X] ALL pull requests should be made against the dev branch!
• [X] Take a look at CONTRIBUTING.MD
• [X] Reference any related issues.
• [X] Provide a description of the proposed changes.
• [ ] PRs must pass Vint tests and add new Vader tests as applicable.
• [X] Make sure to update the documentation in doc/vimwiki.txt if applicable, including the Changelog and Contributors sections.

Hi, I've solved #1007 , the email style arrow quote in vimwiki format conversion to html is working fine. Here's the my test.

Here's the code:

Test arrow quote:

> single arrow
> single arrow line2
> single arrow line3
>> double arrow line
original text
>> double arrow line2
>>>> quater arrow
>>> tripple arrow line
> Jump to single
>>> Jump back to tripple

>> empty line above
>
> empty line with single arrow above

Here's how github display Test arrow quote:

single arrow single arrow line2 single arrow line3

double arrow line original text double arrow line2

quater arrow tripple arrow line Jump to single Jump back to tripple

empty line above

empty line with single arrow above

Here's my test screen shot