Organization, Use of Estimates and Basis of Presentation (Details) - USD ($)	3 Months Ended		9 Months Ended
	Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2016	Jan. 31, 2015
Basic loss per share computation
Net loss attributable to common stockholders	$ (2,412,000)	$ (2,816,000)	$ (7,872,000)	$ (9,463,000)
Weighted Average common shares - basic (in shares)	8,702,237	5,574,447	8,702,237	5,574,244
Basic net loss per share (in dollars per share)	$ (0.28)	$ (0.51)	$ (0.90)	$ (1.70)
Diluted loss per share computation
Net loss attributable to common stockholders	$ (2,412,000)	$ (2,816,000)	$ (7,872,000)	$ (9,463,000)
Less: Gain on derivative warrant liability	0	620,687	0	1,401,314
Loss available to common stockholders	$ (2,412,381)	$ (3,437,152)	$ (7,872,115)	$ (10,863,595)
Weighted Average common shares (in shares)	8,702,237	5,574,447	8,702,237	5,574,244
Incremental shares from assumed exercise of warrants and stock options	0	29,351	0	29,351
Adjusted weighted average share - diluted (in shares)	8,702,237	5,603,798	8,702,237	5,603,595
Diluted net loss per share (in dollars per shares)	$ (0.28)	$ (0.61)	$ (0.90)	$ (1.94)