Note 7 - Options and Warrants to Purchase Common Stock - Summary of the Status of the Warrants Outstanding (Details)	6 Months Ended
	Jun. 30, 2017 $ / shares shares
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | $ / shares	$ 0.36
Warrants Outstanding and Exercisable Number Outstanding (in shares) | shares	3,744,623
Warrants Outstanding and Exercisable Weighted Average Remaining Contractual Life (Year)	3 years 357 days
Exercise Price 1 [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | $ / shares	$ 0.25
Warrants Outstanding and Exercisable Number Outstanding (in shares) | shares	3,283,283
Warrants Outstanding and Exercisable Weighted Average Remaining Contractual Life (Year)	4 years
Exercise Price 2 [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | $ / shares	$ 1.15
Warrants Outstanding and Exercisable Number Outstanding (in shares) | shares	461,340
Warrants Outstanding and Exercisable Weighted Average Remaining Contractual Life (Year)	3 years 302 days