Optimize memory

[johningve]

Various memory optimizations.

Before: profile (1).pb.gz

After: profile.pb.gz

[codecov-commenter]

Codecov Report

Merging #75 (e9ffe83) into master (6152764) will decrease coverage by 2.20%. The diff coverage is 56.18%.

@@            Coverage Diff             @@
##           master      #75      +/-   ##
==========================================
- Coverage   57.81%   55.61%   -2.21%     
==========================================
  Files          70       76       +6     
  Lines        6427     7462    +1035     
==========================================
+ Hits         3716     4150     +434     
- Misses       2424     3006     +582     
- Partials      287      306      +19     

Flag	Coverage Δ
unittests	55.61% <56.18%> (-2.21%)	:arrow_down:

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
consensus/byzantine/byzantine.go	1.92% <0.00%> (-0.21%)	:arrow_down:
crypto/bitfield.go	96.61% <0.00%> (-3.39%)	:arrow_down:
genesis.go	100.00% <ø> (ø)
handel/session.go	0.00% <0.00%> (ø)
internal/cli/run.go	16.12% <0.00%> (ø)
leaderrotation/carousel.go	3.77% <0.00%> (-0.49%)	:arrow_down:
leaderrotation/reputation.go	3.07% <0.00%> (-0.26%)	:arrow_down:
metrics/clientlatency.go	2.63% <0.00%> (-0.94%)	:arrow_down:
metrics/plotting/clientlatency.go	0.00% <0.00%> (ø)
metrics/plotting/reader.go	0.00% <ø> (ø)
... and 73 more

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[meling]

@johningve Could you resolve the conflicts in this PR before I review it?