docs: Adjust README after v5 release

[lukaszsocha2]

No description provided.

[coveralls]

Pull Request Test Coverage Report for Build #5391

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 72.048%

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Totals
Change from base Build #5163:	0.0%
Covered Lines:	8220
Relevant Lines:	11409

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💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build #5375

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.004%) to 72.044%

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Files with Coverage Reduction	New Missed Lines	%
src/main/java/com/box/sdk/RealtimeServerConnection.java	1	77.78%

Totals
Change from base Build #5163:	-0.004%
Covered Lines:	8213
Relevant Lines:	11400

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💛 - Coveralls