style fixes
fix #1550: check for null context in ProcessAttachmentsTask.doInBackground
pass context parameter to ProcessAttachmentsTask constructor
null check for context in addMedia
use emailchecker 0.3
Merge pull request #1605 from wordpress-mobile/issue/1550-npe-ImageHelper.getImageSize

fix #1550 npe image helper.get image size
Merge pull request #1607 from wordpress-mobile/issue/1606-emailchecker-0.3

fix #1606: use emailchecker 0.3