csclient: add Client.Meta method
wip
Added search filter functions.

Added support in the elasticsearch DSL for the
filter functions defined in http://tinyurl.com/qzobc69
Merge pull request #142 from mhilton/search-filters

Added search filter functions.

Added support in the elasticsearch DSL for the
filter functions defined in http://tinyurl.com/qzobc69
csclient: do not panic on bad type
Merge pull request #147 from rogpeppe/063-client-meta

csclient: add Client.Meta method

Also add a Get method.
csclient: implement Client.PutExtraInfo
Merge pull request #150 from rogpeppe/064-client-put-extra-info

csclient: implement Client.PutExtraInfo

Implement PUT to the meta/extra-info endpoint.