Note 9 - Fair Value Measurement - Change in Level 3 Financial Liabilities Fair Value (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Balance, beginning of year	$ (5,126,746)	$ (6,325,092)
Net realized gains/(losses)	0	48,375
Net unrealized gains/(losses) relating to instruments still held at the reporting date	3,111,760	747,404
Net purchases, issuances and settlements	9,248	0
Net transfers in and/or out of Level 3	10,500	402,567
Balance, end of period	(1,995,238)	(5,126,746)
Conversion Feature Liability [Member]
Balance, beginning of year	(1,685,947)	(2,325,730)
Net realized gains/(losses)	0	48,375
Net unrealized gains/(losses) relating to instruments still held at the reporting date	969,108	188,841
Net purchases, issuances and settlements	0	0
Net transfers in and/or out of Level 3	10,500	402,567
Balance, end of period	(706,339)	(1,685,947)
Warrant Liability [Member]
Balance, beginning of year	(3,440,799)	(3,999,362)
Net realized gains/(losses)	0	0
Net unrealized gains/(losses) relating to instruments still held at the reporting date	2,142,652	558,563
Net purchases, issuances and settlements	9,248	0
Net transfers in and/or out of Level 3	0	0
Balance, end of period	$ (1,288,899)	$ (3,440,799)