stop using default headers for accept and content-type; set them per-method instead. needed b/c some upcoming methods (e.g. image upload/download) use non-json req/res
Merge pull request #3 from asadovsky/api

stop using default headers for accept and content-type; set them per-met...
add get-image method to client API
tweak client image API change to use existing constant
Merge pull request #4 from asadovsky/api

add get-image method to client API