Remove Job from implemented entities list

It's not necessary, as Customers are now Jobs if certain attributes are
set.

More info:
https://developer.intuit.com/docs/0025_quickbooksapi/0058_faq/qbo_v2_to_
v3_migration_guide#Jobs_%28subcustomers%29
Merge pull request #35 from harvesthq/remove-job-from-readme

Remove Job from implemented entities list
add current balance & current_balance_with_sub_accounts to Account w/tests
Fixes #36

- update nokogiri runtime dependency to '~> 1.6', '>= 1.6.1'

- bump the gem version
Merge pull request #37 from diego-link-eggy/master

add current balance & with_sub_accounts to Account w/tests
Merge pull request #38 from jleo3/bump_nokogiri_version

Fixes #36
Version bump
Fix spelling, update tutorial link, and add info about changing logger targets
Merge pull request #40 from minimul/readme-update

Fix spelling, update tutorial link, and add info about changing logger targets.
Kept receving a:
```
Fetching source index from http://rubygems.org/
Resolving dependencies...
Bundler could not find compatible versions for gem "nokogiri":
  In Gemfile:
    quickeebooks (>= 0) ruby depends on
      nokogiri (~> 1.5.9) ruby

    nokogiri (1.6.1)
```
.. when trying to bundle in a client project
after updating quickbooks-ruby to the latest. Removing the
pessimistic constraint allowed the bundle to go thru fine.

Let's roll back this change as many apps are going to be running
quickeebooks also.
Merge pull request #41 from minimul/nokogiri

Kept receving a:
Include base_service after service_crud
Include ServiceCrud in BaseService
Remove include ServiceCrud

Its already included in BaseService class
Merge pull request #42 from whereisciao/include-crud-in-base-service

Include crud in base service