Prepare for v5.7.4

update submodule

Update to version 5.6.6

Merge pull request #42 from danielinux/prepare-5.6.0-0

Updating wolfSSL to v5.6.0

Merge pull request #39 from danielinux/v5.5.4-rc

Prepare release 5.5.4

Merge pull request #38 from danielinux/update-v5.5.3

Update to version 5.5.3

Bump version to 5.4.0

Remove dead Travis CI

wolfSSL version updated to v4.1.0-stable

wolfSSL 3.15.7 support