make sure we don't get any query results when an invalid author id or author name is passed in.

see https://github.com/GigaOM/legacy-pro/issues/2043
Merge pull request #18 from wluo/github-2043

detect invalid author name and author id
Add in oxford commas for researc/search in a more durable

See: https://github.com/GigaOM/legacy-pro/issues/2491
Use the $betweenLast variable if set
Merge pull request #19 from borkweb/proper-oxford-commas

Add in oxford commas for researc/search in a more accurate
use go_xpost_post_filter to strip out any coauthors_plus taxonomy terms from the post to be xposted. these terms should be added by co-authors-plus on the destination blog instead of copying the author terms created on the source blog.

see https://github.com/GigaOM/legacy-pro/issues/2045
Merge pull request #20 from wluo/github-2045

strip out redundant coauthors_plus taxonomy terms in xpost data
local coauthors was messing with unsupported post types

The query was being altered by local coauthors plus even if the post type being queried was explicitly unsupported for coauthors.

This resolves a compatibility issues between `go-alerts` and coauthors-plus.  The issue was reported here: https://github.com/GigaOM/legacy-pro/issues/3088
Merge pull request #21 from zbtirrell/better-post-type-exclusions

local coauthors was messing with unsupported post types