Revert "Remove never thrown exceptions."

This reverts commit 820cebf939a8902edc75ee03021085bc16cec6bb.
Revert "Change closed channel sendable status."

This reverts commit f6b6e9367967b7f6ab9becae40b3321f2d4d1942.
Merged omerfarukdemir's commits and started throwing
ChannelClosedException on isSendable and isReceivable
pom version bumped up
updated .gitignore
updated readme