Make get/put more robust

  - init folder if not present already in 'get()' call
  - put.go was referencing wrong args - fix it
  - if no OBJECTNAME is specified during 'get' - grab a
    list of files under "~/.minio"
  - Provide new API GetList() for ObjectStorage struct
Merge pull request #99 from harshavardhana/pr_out_make_get_put_more_robust