harvesting Improve documentation

I realize that examples in the README.md are not the best way to document the behavior of this gem.

It would be great if we could point people to this page so that they could see complete documentation of the librtary: https://www.rubydoc.info/github/ombulabs/harvesting/Harvesting/Client#clients-instance_method

Nov 03 '18 18:11 etagwerker

~~How do you create a single time entry using Harvesting?~~

This was the closest I could get, since I didn't want to use an ENV variable for the access_token:

class HarvestService < ApplicationService
  def initialize(access_token:,account_id:)
    @client = Harvesting::Client.new(access_token: access_token, account_id: account_id)
  end

  def take_day_off(date:)
    entry = Harvesting::Models::TimeEntry.new(
      {
        # user_id: defaults to access token user
        project_id: project.id,
        task_id: task.id,
        spent_date: date,
        started_time: "9:00am",
        ended_time: "5:00pm",
      },
      client: @client
    )
    @client.create(entry)
  end

  protected
    def project(name: )
      @client.projects.entries.first
    end

    def task(name: )
      @client.tasks.entries.first
    end
end

that extra client: option was quite confusing. I'm excited about your TODO.md!