eplusr v0.10.1

This is a patch update mainly to fix CRAN check errors, with few bug fixes.

Bug fixes

• $set() method in Idf class now does not try to convert all input strings
  into numbers (#32)
• $del() method in Idf class now also respects validation settings.
  You should be able to delete any object if current validation level does not
  include reference checking
• $del() method in Idf class now will only print object relation only if
  .ref_to or .ref_by is TRUE
• Now $set() method in Epw class will correctly reset leap year flag in the
  header (#32)
• Now $save() method in Epw class returns the path of saved file invisibly