logbin v2.0.6

• Replace vcov calculation in summary.logbin to replicate the version in summary.glm.
• Implement tests using testthat.
• Clarify the copyright status of functions based on base R.
• (Minor) Removed unused contr.isototonic.rev function. Also no longer exporting interpret.logbin.smooth.
• (Minor) Suppress startup messages when turboEM::turboem is called for the first time.
• (Minor) Update logbin-package Rd file to remove CRAN NOTE.