Merge pull request #1819: rational -> decimal

* changelog

* ...

* decimal func working

* decimal complete, untested

* fixing tests

* decimal compile errors resolved

* test compile errors

* precision multiplier test

* 1% laptop battery

* fixed TestNewDecFromStr

* equalities working

* fix bankers round chop

* ...

* working, some decimal issues resolved

* fix rounding error

* rounding works

* decimal works

* ...

* deleted rational

* rational conversion working

* revert changelog

* code compiles (not tests)

* went through all NewDec, made sure they were converted from NewRat properly

* test debugging

* all testing bugs besides the json marshalling fixed

* json unmarshal

* lint

* document update

* fix lcd test

* cli test fix

* mostly undo Dece -> Rate

* val comments

* Efficiency improvements

This now caches all of the precision multipliers (as they were all
used in non-mutative functions), and caches the precisionInt calculation.
(Now it just copies the already calculated value)

* Cache another precisionInt() call.

* Improve banker rounding efficiency

* remove defer, make negation in-place.

* chris val comments

* bez comments

* Aditya comments

* ...

* val comments

* rebasing start

* ...

* compiling

* tests pass

* cli fix

* anton, cwgoes, val comments

* val and jae comments

* type

* undo reuse quo

client/lcd/test_helpers.go

@@ -173,7 +173,7 @@ func InitializeTestLCD(t *testing.T, nValidators int, initAddrs []sdk.AccAddress
 		accAuth.Coins = sdk.Coins{sdk.NewInt64Coin("steak", 100)}
 		acc := gapp.NewGenesisAccount(&accAuth)
 		genesisState.Accounts = append(genesisState.Accounts, acc)
-		genesisState.StakeData.Pool.LooseTokens = genesisState.StakeData.Pool.LooseTokens.Add(sdk.NewRat(100))
+		genesisState.StakeData.Pool.LooseTokens = genesisState.StakeData.Pool.LooseTokens.Add(sdk.NewDec(100))
 	}
 
 	appState, err := wire.MarshalJSONIndent(cdc, genesisState)