Add filtering option parameters to get_conversion_stats_by_adcampaign method.
Merge branch 'master' into update
Modify parameter default value of by_impression_time of get_conversion_stats_by_adcampaign method.
Merge branch 'master' into update
Merge branch 'master' into update
Add feature for limit and paging to the get_adcampaigns_of_account() method.
Modify return type of get_adcampaigns_of_account() method.
Change __page_result to make_request for backward compatibility.
Merge pull request #26 from taenyon/update

Recover returned data type of some methods.