Use relative path to specify location of Python files

Previously, the layout of my computer's file system was
hard-coded here.

src/harmonicmaps.cc

@@ -130,7 +130,8 @@ int main (int argc, char *argv[])
     //feenableexcept(FE_INVALID);
     Python::runStream()
         << std::endl << "import sys"
-        << std::endl << "sys.path.append('/home/sander/dune/dune-gfe/problems')"
+        << std::endl << "import os"
+        << std::endl << "sys.path.append(os.getcwd() + '/../../problems/')"
         << std::endl;