fix ImmutableArray#++
fix treeLocEqual
improve TreeLocArbitrary
fix TreeLocTest
override zipWithL, zipWithR

avoid infinite loop if stream is infinite
add zipL test
Document unsafeTap name
optimize NonEmptyList#traverse1. avoid stack overflow
add AlignTest
use alignWith instead of align & map

avoid allocate intermediate objects. optimization only, no behavior changes.
add primitive check for ClassCastException in ++ on ImmutableArray
Merge pull request #525

fix ImmutableArray#++
Merge pull request #527 from xuwei-k/treeLocEqual

fix treeLocEqual and improve TreeLocArbitrary
Merge pull request #534 from xuwei-k/infinite-stream-zipWith

override zipWithL, zipWithR
Merge pull request #536 from refried/patch-9

Document unsafeTap name
fix TreeLocArbitrary comments. it is not SI-6854
fix TreeArbitrary

previous version generates too large Tree
enable Tree traverse1 test
Merge pull request #543 from xuwei-k/tree-arb

fix TreeArbitrary. enable Tree traverse1 test
IndexedSeq Align instance