remove dependency on guava

[coveralls]

Pull Request Test Coverage Report for Build 402

• 25 of 29 (86.21%) changed or added relevant lines in 3 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.2%) to 82.639%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/main/java/au/com/southsky/jfreesane/SaneClientAuthentication.java	11	12	91.67%
src/main/java/au/com/southsky/jfreesane/SaneImage.java	12	15	80.0%
<!--	Total:	25	29	86.21%	-->

Files with Coverage Reduction	New Missed Lines	%
src/main/java/au/com/southsky/jfreesane/SaneClientAuthentication.java	1	92.06%
<!--	Total:	1		-->

Totals
Change from base Build 400:	-0.2%
Covered Lines:	952
Relevant Lines:	1152

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💛 - Coveralls