removed `r-cran-tkrplot`: infinite loop!
install tkrplot deps using apt
Revert "install tkrplot deps using apt"

This reverts commit 4b6e07c67ae19440aadbdd580c39c85f28cff706.
Revert "removed `r-cran-tkrplot`: infinite loop!"

This reverts commit d15991668474344eb9ae9012d0300a76534c4923.
add install `r-cran-randomfields`
install `tkrplot` deps via apt: tcltk 8.6, not 8.5
Merge branch 'master' into development

Conflicts:
	.travis.yml