added configurable dragover classname

[mousemke]

closes #26

[coveralls]

Pull Request Test Coverage Report for Build 92

• 3 of 3 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 100.0%

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Totals
Change from base Build 75:	0.0%
Covered Lines:	111
Relevant Lines:	111

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💛 - Coveralls

[mousemke]

upon examination, this actually closes #25 as well

[lifenautjoe]

Great stuff Mouse! Thanks!

[lifenautjoe]

Released @ 2.2.0