Add ProducerOf.apply2/ConsumerOf.apply2 for binary compatibility

[Z1kkurat]

This is continuation of #372 for ConsumerOf/ProducerOf factory methods

[coveralls]

Pull Request Test Coverage Report for Build 5964585693

• 0 of 2 (0.0%) changed or added relevant lines in 2 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.1%) to 76.57%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
skafka/src/main/scala/com/evolutiongaming/skafka/consumer/ConsumerOf.scala	0	1	0.0%
skafka/src/main/scala/com/evolutiongaming/skafka/producer/ProducerOf.scala	0	1	0.0%

Files with Coverage Reduction	New Missed Lines	%
skafka/src/main/scala/com/evolutiongaming/skafka/consumer/ConsumerConfig.scala	1	86.11%

Totals
Change from base Build 5964219619:	-0.1%
Covered Lines:	1366
Relevant Lines:	1784

---

💛 - Coveralls