Summary of Significant Accounting Policies - Calculations of Earnings Per Share (Details) - USD ($)	12 Months Ended
	Apr. 30, 2016	Apr. 30, 2015
Basic loss per share computation
Net loss attributable to common stockholders	$ (10,445,537)	$ (13,139,820)
Weighted Average common shares - basic (in shares)	8,695,199	5,985,346
Basic net loss per share (in dollars per share)	$ (1.20)	$ (2.20)
Diluted loss per share computation
Less: Gain on derivative warrant liability	$ 0	$ 980,519
Loss available to common stockholders	$ (10,445,537)	$ (14,120,339)
Weighted Average common shares (in shares)	8,695,199	5,985,346
Incremental shares from assumed exercise of warrants and stock options (in shares)	0	439,065
Adjusted weighted average share - diluted (in shares)	8,695,199	6,424,411
Diluted net loss per share (in dollars per shares)	$ (1.20)	$ (2.20)