allow badgeos_get_achievement_post_thumbnail() to accept an array for  paramater
allow badgeos_get_achievement_post_thumbnail() to accept an array for  paramater

X-Raym/badgeos,morphatic/badgeos,bethadele/badgeos,opencredit/badgeos,morphatic/badgeos,bethadele/badgeos,X-Raym/badgeos,Sym-O/badgeos,Sym-O/badgeos,opencredit/badgeos,X-Raym/badgeos,bethadele/badgeos,Sym-O/badgeos,morphatic/badgeos,discendum/obf-wordpress,Sym-O/badgeos,X-Raym/badgeos,bethadele/badgeos,discendum/obf-wordpress,discendum/obf-wordpress,discendum/obf-wordpress,morphatic/badgeos,opencredit/badgeos,opencredit/badgeos,opencredit/badgeos