fixed problem that the other's message is missed.
removed unused variable
Merge pull request #52 from haushinka2dx/fix-lack-intermediate-messages

fixed problem that the other's message is missed.
uploadable implemented, but some bug remains.
enabled to upload, preview, view image, and download
fixed issue that dropzone was not initialised when sender panel's stay
open was "ON"
Merge pull request #53 from haushinka2dx/uploadable

Uploadable
Merge branch 'master' into starter