fix reverse relation bug (#16)
fix reverse relation bug (#16)

* fix reverse relation bugs

1. fix the major bug that we do not consider revverse relation in line
2. consider the special case "mode"
3. consider other special cases "prep-on-behalf-of", "prep-out-of", "consist-of", "subset-of"

* update description

* Update amr.py

* Update amr.py

snowblink14/smatch