v0.1.1

1. linkage for VA
2. add * of ICD codes
   * The ICD code maps exclusively to a specific Phecode (XXX.XX or XXX.X) and not its parent Phecode
   ** The ICD code maps to both Phecode XXX.XX and its parent Phecode XXX.X, but does not map to XXX
3. add G: for ICD groups
   G: ICD node with a prefix G: indicates ICD group that include children ICD codes, and can be expanded