Cherry-pick types/rat: Fix overflowing in printing

This now uses the underlying golang big.rat's string function,
instead of casting to num and den which are int64s.

Closes #1258

CHANGELOG.md

@@ -1,5 +1,39 @@
 # Changelog
 
+## 0.20.0
+
+*TBD*
+
+BREAKING CHANGES
+* Change default ports from 466xx to 266xx
+* AltBytes renamed to Memo, now a string, max 100 characters, costs a bit of gas
+* Transactions now take a list of Messages
+* Signers of a transaction now only sign over their account and sequence number
+* Removed MsgChangePubKey from auth
+* Removed setPubKey from account mapper
+
+FEATURES
+* [gaiacli] You can now attach a simple text-only memo to any transaction, with the `--memo` flag
+* [lcd] Queried TXs now include the tx hash to identify each tx
+* [mockapp] CompleteSetup() no longer takes a testing parameter
+* [governance] Implemented MVP
+  * Supported proposal types: just binary (pass/fail) TextProposals for now
+  * Proposals need deposits to be votable; deposits are burned if proposal fails
+  * Delegators delegate votes to validator by default but can override (for their stake)
+* [tools] make get_tools installs tendermint's linter, and gometalinter
+* [tools] Switch gometalinter to the stable version
+* [tools] Add checking for misspellings and for incorrectly formatted files in circle CI
+* [server] Default config now creates a profiler at port 6060, and increase p2p send/recv rates
+
+FIXES
+* \#1259 - fix bug where certain tests that could have a nil pointer in defer
+* \#1052 - Make all now works
+* Retry on HTTP request failure in CLI tests, add option to retry tests in Makefile
+* Fixed bug where chain ID wasn't passed properly in x/bank REST handler
+* Fixed bug where `democli account` didn't decode the account data correctly
+* \#1343 - fixed unnecessary parallelism in CI
+* \#1258 - printing big.rat's can no longer overflow int64
+
 ## 0.19.0
 
 *June 13, 2018*

types/rational.go

@@ -91,7 +91,7 @@ func (r Rat) Mul(r2 Rat) Rat    { return Rat{*new(big.Rat).Mul(&(r.Rat), &(r2.Ra
 func (r Rat) Quo(r2 Rat) Rat    { return Rat{*new(big.Rat).Quo(&(r.Rat), &(r2.Rat))} } // Quo - quotient
 func (r Rat) Add(r2 Rat) Rat    { return Rat{*new(big.Rat).Add(&(r.Rat), &(r2.Rat))} } // Add - addition
 func (r Rat) Sub(r2 Rat) Rat    { return Rat{*new(big.Rat).Sub(&(r.Rat), &(r2.Rat))} } // Sub - subtraction
-func (r Rat) String() string    { return fmt.Sprintf("%v/%v", r.Num(), r.Denom()) }
+func (r Rat) String() string    { return r.Rat.String() }
 
 var (
 	zero  = big.NewInt(0)

types/rational_test.go

@@ -100,7 +100,7 @@ func TestEqualities(t *testing.T) {
 
 }
 
-func TestArithmatic(t *testing.T) {
+func TestArithmetic(t *testing.T) {
 	tests := []struct {
 		r1, r2                         Rat
 		resMul, resDiv, resAdd, resSub Rat
@@ -297,3 +297,14 @@ func TestRatsEqual(t *testing.T) {
 	}
 
 }
+
+func TestStringOverflow(t *testing.T) {
+	// two random 64 bit primes
+	rat1 := NewRat(5164315003622678713, 4389711697696177267)
+	rat2 := NewRat(-3179849666053572961, 8459429845579852627)
+	rat3 := rat1.Add(rat2)
+	assert.Equal(t,
+		"29728537197630860939575850336935951464/37134458148982045574552091851127630409",
+		rat3.String(),
+	)
+}