fs v1.2.2

Features

• fs no longer needs a C++11 compiler, it now works with compilers which
  support only C++03 (#90).

Bugfixes

• fs_path fs_bytes and fs_perm objects now use methods::setOldClass()
  so that S4 dispatch to their base classes works as intended (#91).

• Fix allocation bug in path_exists() using delete [] when we should have
  used free().