CBLJSON should use milliseconds in ISO-8601 dates
CBLJSON should use milliseconds in ISO-8601 dates

CBLJSON was using an ISO-8601 date format string without milliseconds in it.
But ECMAScript specifies that date strings should have milliseconds.
I extended the code to (a) generate strings with millis, and (b) parse strings with or without them.
Added a test case, too.
Fixes #33.

couchbase/couchbase-lite-ios,ipmobiletech/couchbase-lite-ios,ryuzmukhametov/couchbase-lite-ios,evsukov89/couchbase-lite-ios,pegli/couchbase-lite-ios,mz2/couchbase-lite-ios,Chavenay/couchbase-lite-ios,amco/couchbase-lite-ios,ipmobiletech/couchbase-lite-ios,brendand/couchbase-lite-ios,pegli/couchbase-lite-ios,ryuzmukhametov/couchbase-lite-ios,Chavenay/couchbase-lite-ios,gotmyjobs/couchbase-lite-ios,macoscope/couchbase-lite-ios,couchbase/couchbase-lite-ios,ryuzmukhametov/couchbase-lite-ios,brendand/couchbase-lite-ios,Chavenay/couchbase-lite-ios,couchbase/couchbase-lite-ios,macoscope/couchbase-lite-ios,gotmyjobs/couchbase-lite-ios,pegli/couchbase-lite-ios,couchbase/couchbase-lite-ios,brendand/couchbase-lite-ios,alfared/couchbase-lite-ios,pegli/couchbase-lite-ios,lordkev/couchbase-lite-ios,amco/couchbase-lite-ios,amco/couchbase-lite-ios,mz2/couchbase-lite-ios,mz2/couchbase-lite-ios,jkingyens/couchbase-lite-ios,myDario/couchbase-lite-ios,brendand/couchbase-lite-ios,brendand/couchbase-lite-ios,tomco/couchbase-lite-ios,evsukov89/couchbase-lite-ios,pellekrogholt/couchbase-lite-ios,amco/couchbase-lite-ios,myDario/couchbase-lite-ios,amco/couchbase-lite-ios,alfared/couchbase-lite-ios,macoscope/couchbase-lite-ios,lordkev/couchbase-lite-ios,tomco/couchbase-lite-ios,gotmyjobs/couchbase-lite-ios,couchbase/couchbase-lite-ios,jkingyens/couchbase-lite-ios,pellekrogholt/couchbase-lite-ios,couchbase/couchbase-lite-ios,myDario/couchbase-lite-ios,macoscope/couchbase-lite-ios,gotmyjobs/couchbase-lite-ios,alfared/couchbase-lite-ios,jkingyens/couchbase-lite-ios,amco/couchbase-lite-ios,lordkev/couchbase-lite-ios,lordkev/couchbase-lite-ios,ryuzmukhametov/couchbase-lite-ios,jkingyens/couchbase-lite-ios,tomco/couchbase-lite-ios,ipmobiletech/couchbase-lite-ios,tomco/couchbase-lite-ios,alfared/couchbase-lite-ios,ipmobiletech/couchbase-lite-ios,pellekrogholt/couchbase-lite-ios,amco/couchbase-lite-ios,pellekrogholt/couchbase-lite-ios,evsukov89/couchbase-lite-ios