Stock-Based Compensation - Stock-based compensation expense (Details) - USD ($)
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Stock-Based Compensation      
Total stock-based compensation expense $ 1,841,901 $ 1,220,118 $ 724,063
Cost of revenue      
Stock-Based Compensation      
Total stock-based compensation expense 147,400 77,771 6,529
General and administrative      
Stock-Based Compensation      
Total stock-based compensation expense 1,144,207 541,876 266,167
Sales and marketing      
Stock-Based Compensation      
Total stock-based compensation expense 493,362 555,478 415,021
Research and development      
Stock-Based Compensation      
Total stock-based compensation expense $ 56,932 $ 44,993 $ 36,346