Use consistent variable name casing

[Lars Willighagen]

This may be a bit nitpicky, but if you're using standard, you should also use camelCase, even if the linter has a hard time enforcing that rule. Example:

if (eupmc.hitlimit - eupmc.allresults.length < eupmc.pagesize) {
  eupmc.residualhits = eupmc.hitlimit - eupmc.allresults.length
}

Whereas the next line does use camelCase.

eupmc.nextCursorMark = resp.nextCursorMark[0]

https://github.com/ContentMine/getpapers/blob/master/lib/eupmc.js#L160-L163