Note 5 - Summary of Option Activity for Employees and Non-Employees (Details) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2015
Employee Stock Option [Member]
Number of options, beginning balance (in shares)	1,419,436
Weighted average exercise price, beginning balance (in dollars per share)	$ 1.56
Weighted average remaining contractual life, beginning balance	2 years 270 days	2 years 284 days
Aggregate intrinsic value, beginning balance	$ 1,220,338
Number of options granted (in shares)	348,908
Weighted average exercise price, granted (in dollars per share)	$ 1.72
Weighted average remaining contractual life, granted	4 years 310 days
Number of options exercised (in shares)
Number of options forfeited and expired (in shares)
Number of options, ending balance (in shares)	1,768,344	1,419,436
Weighted average exercise price, ending balance (in dollars per share)	$ 1.59	$ 1.56
Aggregate intrinsic value, ending balance	$ 2,099,051	$ 1,220,338
Number of options, exercisable (in shares)	1,170,718
Weighted average exercise price, exercisable (in dollars per share)	$ 1.36
Weighted average remaining contractual life, exercisable	2 years 156 days
Aggregate intrinsic value, exercisable	$ 1,721,587
Non-employee Options [Member]
Number of options, beginning balance (in shares)	8,333
Weighted average exercise price, beginning balance (in dollars per share)	$ 2.70
Weighted average remaining contractual life, beginning balance	4 years 211 days	4 years 302 days
Number of options granted (in shares)	200,000
Weighted average exercise price, granted (in dollars per share)	$ 2.55
Weighted average remaining contractual life, granted	1 year 215 days
Number of options exercised (in shares)
Number of options forfeited and expired (in shares)
Number of options, ending balance (in shares)	208,333	8,333
Weighted average exercise price, ending balance (in dollars per share)	$ 2.56	$ 2.70
Aggregate intrinsic value, ending balance	$ 50,833
Number of options, exercisable (in shares)	2,777
Weighted average exercise price, exercisable (in dollars per share)	$ 2.70
Weighted average remaining contractual life, exercisable	4 years 120 days
Aggregate intrinsic value, exercisable	$ 0