Add unit tests for parseRFC822DateTimeString and toRFC822DateTimeString.
Add unit tests for parseRFC822DateTimeString and toRFC822DateTimeString.

fast4shoot/vibe.d,machindertechnologies/vibe.d,yannick/vibe.d,etcimon/vibe.d,nathanchristenson/vibe.d,schuetzm/vibe.d,jkm/vibe.d,sigod/vibe.d,jkm/vibe.d,Yoplitein/vibe.d,Mihail-K/vibe.d,redstar/vibe.d,gedaiu/vibe.d,sigod/vibe.d,etcimon/vibe.d,etcimon/vibe.0,alphaKAI/vibe.d,dkillebrew/vibe.d,etcimon/vibe.0,Yoplitein/vibe.d,alphaKAI/vibe.d,alphaKAI/vibe.d,AndreyMZ/vibe.d,Kozzi11/vibe.d,ColdenCullen/vibe.d,mfrischknecht/vibe.d,nathanchristenson/vibe.d,nathanchristenson/vibe.d,Yoplitein/vibe.d,sigod/vibe.d,rejectedsoftware/vibe.d,veelo/vibe.d,chalucha/vibe.d,DBankov/vibe.d,Geod24/vibe.d