Note 13 - Equity Incentive Plans - Stock Option Activity (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017	Dec. 31, 2016
Number of shares (in shares)	5,275,000	1,225,000
Weighted average exercise price (per share) (in dollars per share)	$ 0.26	$ 0.17
Weighted average remaining contractual term (in years) (Year)	3 years 211 days	4 years 32 days	2 years 226 days
Aggregate intrinsic value	$ 396,500	$ 130,475	$ 83,425
Number of shares, granted (in shares)	570,000	4,650,000
Weighted average exercise price (per share), granted (in dollars per share)	$ 0.28	$ 0.26
Number of shares, exercised (in shares)	(200,000)	(300,000)
Weighted average exercise price (per share), exercised (in dollars per share)	$ 0.22	$ 0.13
Number of shares, forfeited/cancelled/expired (in shares)	(2,975,000)	(300,000)
Weighted average exercise price (per share), forfeited/cancelled/expired (in dollars per share)	$ 0.25	$ 0.14
Number of shares (in shares)	2,670,000	5,275,000	1,225,000
Weighted average exercise price (per share) (in dollars per share)	$ 0.27	$ 0.26	$ 0.17
Vested and exercisable at September 30, 2018 (in shares)	800,000
Vested and exercisable at September 30, 2018 (in dollars per share)	$ 0.22
Vested and exercisable at September 30, 2018 (Year)	2 years 208 days
Vested and exercisable at September 30, 2018	$ 158,425