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Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity (Schedule of Stock Options Activity) (Details)

v3.8.0.1
Stockholders' Equity (Schedule of Stock Options Activity) (Details) - Stock Incentive Plan and Stock Option Grants to Employees and Directors [Member]
 9 Months Ended
Jan. 31, 2018
USD ($)
$ / shares
shares
Number of Shares  
Balance Outstanding, April 30, 2017 | shares 2,097,384
Granted | shares 844,000
Exercised | shares (63,838)
Forfeited | shares
Expired | shares
Balance Outstanding, January 31, 2018 | shares 2,877,546
Exercisable, January 31, 2018 | shares 1,083,484
Weighted Average Exercise Price  
Balance Outstanding, April 30, 2017 | $ / shares $ 1.86
Granted | $ / shares 3.53
Exercised | $ / shares 3.13
Forfeited | $ / shares
Expired | $ / shares
Balance Outstanding, January 31, 2018 | $ / shares 3.52
Exercisable, January 31, 2018 | $ / shares $ 2.22
Balance Outstanding, April 30, 2017 2 years 8 months 12 days
Granted 3 years 4 months 24 days
Balance Outstanding, January 31, 2018 3 years 2 months 27 days
Exercisable, January 31, 2018 2 years 26 days
Aggregate Intrinsic Value  
Balance Outstanding, April 30, 2017 | $ $ 12,489,871
Granted | $ 1,867,740
Forfeited | $
Balance Outstanding, January 31, 2018 | $ 17,658,268
Exercisable, January 31, 2018 | $ $ 8,727,757