Note 8 - Net Loss Per Share - Schedule of Earnings Per Share (Details) - USD ($)	3 Months Ended			6 Months Ended	9 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2017	Jun. 30, 2018	Sep. 30, 2018	Sep. 30, 2017
Net loss	$ (3,309,866)		$ (2,184,510)		$ (9,326,825)	$ (6,129,553)
Deemed dividend attributable to preferred stock		$ (11,479,308)		$ (11,479,308)	(11,479,308)	(2,568,132)
Net loss applicable to common stockholders	$ (3,309,866)	$ (15,621,885)	$ (2,184,510)	$ (17,496,267)	$ (20,806,133)	$ (8,697,685)
Weighted average shares outstanding - basic and diluted (in shares)	5,183,492		1,034,262		3,645,682	657,184
Loss per common share -basic and diluted (in dollars per share)	$ (0.64)	$ (5.08)	$ (2.11)	$ (6.11)	$ (5.71)	$ (13.23)