async login (data) {
    return await this._fetch({
      method: 'POST',
      url: '/account/login',
      body: data
    })
      .then((res) => {
        if (res.status === 200 || res.status === 201) {
          return res.json
        } else {
          throw (res.json)
        }
      })
      .catch((error) => {
        throw (error)
      })
  }
### login
encode the data and and call _fetch

@param data

 {username: "barton", password: "Passw0rd!"}

@returns

createdAt: "2015-12-30T15:29:36.611Z"
updatedAt: "2015-12-30T16:08:50.419Z"
objectId: "Z4yvP19OeL"
email: "barton@foo.com"
sessionToken: "r:Kt9wXIBWD0dNijNIq2u5rRllW"
username: "barton"