Add param natspec to UnitConversionUtils methods

Author: cgewecke

contracts/lib/UnitConversionUtils.sol

@@ -35,6 +35,10 @@ library UnitConversionUtils {
      * @dev Converts a uint256 PRECISE_UNIT quote quantity into an alternative decimal format.
      *
      * This method is borrowed from PerpProtocol's `lushan` repo in lib/SettlementTokenMath
+     *
+     * @param _amount       PRECISE_UNIT amount to convert from
+     * @param _decimals     Decimal precision format to convert to
+     * @return              Input converted to alternative decimal precision format
      */
     function fromPreciseUnitToDecimals(uint256 _amount, uint8 _decimals) internal pure returns (uint256) {
         return _amount.div(10**(18 - uint(_decimals)));
@@ -44,13 +48,21 @@ library UnitConversionUtils {
      * @dev Converts an int256 PRECISE_UNIT quote quantity into an alternative decimal format.
      *
      * This method is borrowed from PerpProtocol's `lushan` repo in lib/SettlementTokenMath
+     *
+     * @param _amount       PRECISE_UNIT amount to convert from
+     * @param _decimals     Decimal precision format to convert to
+     * @return              Input converted to alternative decimal precision format
      */
     function fromPreciseUnitToDecimals(int256 _amount, uint8 _decimals) internal pure returns (int256) {
         return _amount.div(int256(10**(18 - uint(_decimals))));
     }
 
     /**
      * @dev Converts an arbitrarily decimalized quantity into a PRECISE_UNIT quantity.
+     *
+     * @param _amount       Non-PRECISE_UNIT amount to convert
+     * @param _decimals     Decimal precision of amount being converted to PRECISE_UNIT
+     * @return              Input converted to PRECISE_UNIT decimal format
      */
     function toPreciseUnitsFromDecimals(int256 _amount, uint8 _decimals) internal pure returns (int256) {
         return _amount.mul(int256(10**(18 - (uint(_decimals)))));