Note 8 - Options and Warrants to Purchase Common Stock - Summary of the Status of the Warrants Outstanding (Details) - $ / shares	3 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Warrants Outstanding and Exercisable Number Outstanding (in shares)	3,744,623
Warrants Outstanding and Exercisable Weighted Average Remaining Contractual Life (Year)	4 years 91 days
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)	$ 0.36	$ 0.25
Exercise Price 1 [Member]
Warrants Outstanding and Exercisable Number Outstanding (in shares)	3,283,283
Warrants Outstanding and Exercisable Weighted Average Remaining Contractual Life (Year)	4 years 91 days
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)	$ 0.25
Exercise Price 2 [Member]
Warrants Outstanding and Exercisable Number Outstanding (in shares)	461,340
Warrants Outstanding and Exercisable Weighted Average Remaining Contractual Life (Year)	4 years 18 days
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)	$ 1.15