update Gopkg.toml and update dependencies

[CoderZhi]

Fix a bug in iotex-election, and update the revision number correspondingly.
dep ensure -update github.com/iotexproject/iotex-election
somehow iotexproject/go-ethereum get updated as well.
All db files should be deleted with this pr.

Test plan: make test & make minicluster

[codecov]

Codecov Report

Merging #662 into master will increase coverage by 0.28%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #662      +/-   ##
==========================================
+ Coverage   60.06%   60.34%   +0.28%     
==========================================
  Files         132      135       +3     
  Lines       12561    12920     +359     
==========================================
+ Hits         7545     7797     +252     
- Misses       3974     4046      +72     
- Partials     1042     1077      +35

Impacted Files	Coverage Δ
pkg/keypair/keypair.go	65.21% <0%> (-8.98%)	⬇️
blockchain/blockchain.go	49.55% <0%> (-0.07%)	⬇️
crypto/bls.go	61.18% <0%> (ø)
crypto/dkg.go	81.03% <0%> (ø)
crypto/ec160.go	71.15% <0%> (ø)
pkg/keypair/secp256k1.go	90.9% <0%> (+7.57%)	⬆️

---

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Δ = absolute <relative> (impact), ø = not affected, ? = missing data
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[codecov]

Codecov Report

Merging #662 into master will increase coverage by 0.28%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #662      +/-   ##
==========================================
+ Coverage   60.06%   60.34%   +0.28%     
==========================================
  Files         132      135       +3     
  Lines       12561    12920     +359     
==========================================
+ Hits         7545     7797     +252     
- Misses       3974     4046      +72     
- Partials     1042     1077      +35

Impacted Files	Coverage Δ
pkg/keypair/keypair.go	65.21% <0%> (-8.98%)	⬇️
blockchain/blockchain.go	49.55% <0%> (-0.07%)	⬇️
crypto/bls.go	61.18% <0%> (ø)
crypto/dkg.go	81.03% <0%> (ø)
crypto/ec160.go	71.15% <0%> (ø)
pkg/keypair/secp256k1.go	90.9% <0%> (+7.57%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 613ec83...1500e3e. Read the comment docs.