Note 14 - Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2017

Notes Tables

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]

	December 31, 2017
	(Level 1)		(Level 2)		(Level 3)
Assets
Cash and cash equivalents	$	8,896,468	$	—	$	—
Liabilities
Common stock warrant liability	$	—	$	—	$	—

	December 31, 2016
	(Level 1)		(Level 2)		(Level 3)
Assets
Cash and cash equivalents	$	1,552,852	$	—	$	—
Liabilities
Common stock warrant liability	$	—	$	—	$	—

Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]

	Common Stock Warrant Liability
Balance at December 31, 2016	$	—
Issued in connection with the Series A convertible preferred stock		35,225,846
Change in fair value		(22,072,322	)
Reclassification of Series A warrants to additional paid in capital		(13,153,524	)
Balance at December 31, 2017	$	—

Schedule of Stockholders' Equity Note, Warrants or Rights [Table Text Block]

Stock price	$	1.44
Exercise price	$	2.22
Expected term (in years)		4.38
Risk-free interest rate		1.9	%
Expected volatility		104.1	%
Dividend yield		—