Stockholders' equity - Company Recognized Stock Compensation Expense (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense	$ 209,307	$ 266,399	$ 454,712	$ 527,896
Cost of Services [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense	2,145	696	3,968	5,008
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense	52,777	73,204	110,555	135,422
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense	160,419	177,025	312,895	349,128
Sales and Marketing [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense	$ (6,034)	$ 15,474	$ 27,294	$ 38,338