Remove character(0) warnings when running devtools::load_all(“.”)

[andrie]

This question at StackOverflow provides a hint:

http://stackoverflow.com/questions/26104401/character0-warnings-when-running-devtoolsload-all-in-rstudio

empty warnings that load_all is giving you are actually initiated when loading the package because of function name conflicts

Conflicts exist in @import tools and we should use @importFrom tools ... instead.