Note 12 - Subsequent Events - Balance Sheet Effects of Warrants Reclassified from Liabilities to Stockholders' Equity (Details) - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Total assets	$ 28,327,243	$ 17,484,384
Total liabilities	21,970,547	8,299,700
Convertible preferred stock, $0.001 par value: Series A - 13,750,000 shares authorized, 12,376,329 and 8,324,032 shares issued and outstanding, respectively at September 30, 2017; No shares authorized, issued or outstanding at December 31, 2016 (liquidation value of $16,814,360 at September 30, 2017)	0	0
Stockholders' equity
Common stock	14,504	10,346
Additional paid-in capital	69,686,744	69,363,575
Accumulated deficit	(63,344,552)	(60,189,237)
Total stockholders' equity	6,356,696	9,184,684
Total liabilities, convertible preferred stock and stockholders' equity	28,327,243	$ 17,484,384
Adjustments for Pro Forma [Member]
Total assets
Total liabilities	(16,316,054)
Convertible preferred stock, $0.001 par value: Series A - 13,750,000 shares authorized, 12,376,329 and 8,324,032 shares issued and outstanding, respectively at September 30, 2017; No shares authorized, issued or outstanding at December 31, 2016 (liquidation value of $16,814,360 at September 30, 2017)
Stockholders' equity
Common stock
Additional paid-in capital	13,153,524
Accumulated deficit	3,162,530
Total stockholders' equity	16,316,054
Total liabilities, convertible preferred stock and stockholders' equity
Pro Forma [Member]
Total assets	28,327,243
Total liabilities	5,654,493
Convertible preferred stock, $0.001 par value: Series A - 13,750,000 shares authorized, 12,376,329 and 8,324,032 shares issued and outstanding, respectively at September 30, 2017; No shares authorized, issued or outstanding at December 31, 2016 (liquidation value of $16,814,360 at September 30, 2017)
Stockholders' equity
Common stock	14,504
Additional paid-in capital	82,840,268
Accumulated deficit	(60,182,022)
Total stockholders' equity	22,672,750
Total liabilities, convertible preferred stock and stockholders' equity	$ 28,327,243