Remove obsolete roadmap file

[ethanfrey]

Closes #258

The file is obsolete, from 6 months ago.
We have acheived many of these points (minus benchmarking) and also some other bns features.

If there are any questions on the roadmap, just ask

[codecov-io]

Codecov Report

Merging #340 into master will decrease coverage by 0.4%.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           master    #340     +/-   ##
========================================
- Coverage    70.4%   69.9%   -0.5%     
========================================
  Files         131     135      +4     
  Lines        6208    6452    +244     
========================================
+ Hits         4374    4514    +140     
- Misses       1414    1495     +81     
- Partials      420     443     +23

Impacted Files	Coverage Δ
commands/server/init.go	71.4% <0%> (ø)
commands/server/retry.go	0% <0%> (ø)
commands/server/getblock.go	4.4% <0%> (ø)
commands/server/start.go	60% <0%> (ø)
cmd/bnsd/client/client.go	53.9% <0%> (+3.7%)	⬆️
cmd/bnsd/client/keys.go	71% <0%> (+5.2%)	⬆️
cmd/bnsd/app/app.go	93.8% <0%> (+7.6%)	⬆️
app/store.go	69.6% <0%> (+11.1%)	⬆️
cmd/bnsd/client/tx.go	85.7% <0%> (+25%)	⬆️
cmd/bnsd/app/init.go	76.7% <0%> (+27.3%)	⬆️
... and 2 more

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