Changed plus/minus to right arrow/down arrow to show affiliation

[alexdryden]

This closes #59. This is just the alternative symbols we used to avoid potential confusion where the + as superscript after a name may seem to indicate that an author is deceased. I used a thin space between the name and the symbol for the sake of expediency, but you may prefer spacing be adjusted with a style rule. Example below:

[Vitaliy-1]

@alexdryden, thanks for the PR, can you re-size and place this symbol similar to a plus/minus signs? I mean top-right position in relation to author and 1-2 px smaller?

[Vitaliy-1]

Also, I'd like to see the symbol solidly white.

[alexdryden]

@Vitaliy-1 sure thing. Here are the changes you asked for:

[Vitaliy-1]

Thanks!