Update README with latest release, nightlies and API docs

Updated stable release links to v3.0.1
Added link to automated dev builds
Changed API link to api.haxe.org
Fixed typo in Community section
this.matchSub should be this.match
remove pf_can_init_member and always move every member initialization to the constructor (closes #2349)
hide abstract member fields from static completion (closes #2351)
temp As3 fix
handle TVars in explode_expressions and consider TTry complex