v2.7.0 - return stresses of predict_mixture()

description

Version 2.7.0

• Make predict_mixture() return the stresses.
• One minor spelling fix.

system details

• RStudio Version: 1.3.938
• R Version: 3.6.3
• OS Version: Windows 10 x64 (build 18363)

checklist

• This merge introduces new features.
  • new features are documented
  • new features have tests
• update documentation including examples (if necessary)
• update and polish NEWS.md
• update version in DESCRIPTION
• update date in DESCRIPTION
• no remaining TODO, FIXME, or debug prints anywhere in the source files
• devtools::document()
• devtools::check() without errors or warnings