Update module version to 1.8.1

Updates latest release notes [ci skip]

Addressing scenarios where filepath is missing from stack trace madal…

…inoprea#51

Fixes e-mail capture for Magento CE 1.7 and Magento EE 1.12 madalinop…

…rea#75

Adds log about recursive rendered block madalinoprea#68

Updates version to 1.6.0

Updates version number and add version changelog

Updates unit tests so that we store durations as real misliseconds

Adds changelog for 1.4.1 version

Update README.md