Merge pull request #649 from gmarz/master

Mtermvectors descriptor can now accept a collection of documents
remove ids from querystring on multitermvector
Merge branch 'master' of github.com:elasticsearch/elasticsearch-net
fix #648 little addendum to @gmarz's work on #649 allowing a an enumerable of documents to passed in, no longer pass ids over querystring but instead always translate them to documents inside the POST body internally
#fix 643 numeric terms we're not showing up on .Key on buckets (null)