Chain combinator operands swap

It seems more natural to have higher-order enumerator on the right
(similar to monadic bind, as pointed out by the reviewers for the
Scala'14 paper)
Benchmarks for measuring memoization effects

Benchmarks for Binary Search Trees without memoization
Benchmark run command 'bench slow' (note: for larger sizes the run may
take long time to finish)
Tests for measuring enumeration times for without memoization are
deprecated
Merge branch 'feat/showcase' into develop

Conflicts:
	src/bench/test/scala/insynth/enumeration/benchmarks/BenchmarkSuite.scala