Note 11 - Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2017

Notes Tables

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

	September 30, 2017
	(Level 1)		(Level 2)		(Level 3)
Assets
Cash and cash equivalents	$	1,216,000	$	—	$	—
Certificate of deposit	$	10,020,164
Liabilities
Common stock warrant liability	$	—	$	—	$	16,316,054

	December 31, 2016
	(Level 1)		(Level 2)		(Level 3)
Assets
Cash and cash equivalents	$	1,552,852	$	—	$	—

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		(18,909,792	)
Balance at September 30, 2017	$	16,316,054

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

Stock price	$	1.66
Exercise price	$	2.22
Expected term (in years)		4.5
Risk-free interest rate		1.8	%
Expected volatility		109.3	%
Dividend yield		—