Note 3 - Schedule of Listing of Stock Options and Warrants (Details) - $ / shares	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Mar. 31, 2014
Stock Options 2011 [Member] | Minimum [Member]
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price	$ 0.75
Stock Options 2011 [Member] | Maximum [Member]
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price	$ 11.20
Stock Options 2011 [Member]
Shares, options (in shares)	11,666
Stock Options 2012 [Member] | Minimum [Member]
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price	$ 5.25
Stock Options 2012 [Member] | Maximum [Member]
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price	$ 6
Stock Options 2012 [Member]
Shares, options (in shares)	126,029
Stock Options 2013 [Member] | Minimum [Member]
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price	$ 4.875
Stock Options 2013 [Member] | Maximum [Member]
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price	$ 23.85
Stock Options 2013 [Member]
Shares, options (in shares)	232,756
Stock Options 2014 [Member] | Minimum [Member]
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price	$ 6.50
Stock Options 2014 [Member] | Maximum [Member]
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price	$ 18.75
Stock Options 2014 [Member]
Shares, options (in shares)	59,013
Stock Options 2015 [Member] | Minimum [Member]
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price	$ 2.63
Stock Options 2015 [Member] | Maximum [Member]
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price	$ 3.45
Stock Options 2015 [Member]
Shares, options (in shares)	321,458
Stock Options 2016 [Member]
Shares, options (in shares)	117,648
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price	$ 0.17
Warrants 2012 [Member] | Minimum [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights
Warrants 2012 [Member]
Class of Warrant or Right, Outstanding	69,801
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 11.25
Warrants 2013 [Member] | Minimum [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights	3.75
Warrants 2013 [Member] | Maximum [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 14.85
Warrants 2013 [Member]
Class of Warrant or Right, Outstanding	267,579
Warrants 2014 [Member] | Minimum [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 9.75
Warrants 2014 [Member] | Maximum [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 24.375
Warrants 2014 [Member]
Class of Warrant or Right, Outstanding	161,375
Warrants 2015 [Member] | Minimum [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 4.95
Warrants 2015 [Member] | Maximum [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 9.75
Warrants 2015 [Member]
Class of Warrant or Right, Outstanding	2,832,317
Minimum [Member]
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price	$ 0.17	$ 0.275	$ 3.2006
Class of Warrant or Right, Exercise Price of Warrants or Rights	3.75
Maximum [Member]
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price	23.85	$ 5.5695	$ 13.9195
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 24.375
Shares, options (in shares)	868,570
Class of Warrant or Right, Outstanding	3,331,072
Class of Warrant or Right, Exercise Price of Warrants or Rights				$ 11.25