Note 10 - Net Loss Per Share - Schedule of Earnings Per Share (Details) - USD ($)	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2018	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Net loss			$ (11,404,934)	$ (8,122,581)
Deemed dividend attributable to preferred stock	$ (11,479,308)	$ (11,479,308)	(11,479,308)	(2,568,132)
Net loss attributable to common shareholders	$ (15,621,885)	$ (17,496,267)	$ (22,884,242)	$ (10,690,713)
Weighted average shares outstanding - basic and diluted (in shares)			4,157,746	974,773
Loss per common share -basic and diluted (in dollars per share)	$ (5.08)	$ (6.11)	$ (5.50)	$ (10.97)