Porting Backlog issues to YAML

(Implemented by python)

Usage

$ git clone https://github.com/nijibox/backlog2x.git
$ cd ./backlog2x
$ cp example.ini app.ini
$ vi app.ini
(Change your Space ID and API Key)
$ ./backlog2x PROJ
(Print issues in PROJ)
$ ./backlog2x PROJ-1
(Dump detail, comments and attachments from issue PROJ-1)
$ ./backlog2x PROJ
(Try to dump detail, comments and attachments from all issues in PROJ)