Init httpclient and dockerclient

[at15]

This PR should implement the basic functionality for #37 , auto encoding/decoding, error handling based on status code etc.

Basic

• [x] decode response to struct when it's json
• [x] error handler based on http code
• [ ] allow save request/response to context

Advanced (optional)

• [ ] retry policy

Docker client

The command is now called dk ...

• [x] version, ping
• [ ] images
• [ ] containers
• [ ] stream log
• [ ] events
• [ ] stats

[codecov-io]

Codecov Report

Merging #39 into master will increase coverage by 12.37%. The diff coverage is 49.06%.

@@            Coverage Diff             @@
##           master     #39       +/-   ##
==========================================
+ Coverage   32.82%   45.2%   +12.37%     
==========================================
  Files          12       6        -6     
  Lines         131     250      +119     
==========================================
+ Hits           43     113       +70     
- Misses         85     110       +25     
- Partials        3      27       +24

Impacted Files	Coverage Δ
httpclient/method.go	100% <100%> (ø)
httpclient/option.go	30.43% <30.43%> (ø)
httpclient/util.go	35.29% <35.29%> (ø)
httpclient/client.go	35.59% <38.53%> (ø)
httpclient/context.go	35.55% <44.44%> (ø)
httpclient/error.go	78.26% <78.26%> (ø)
ice/db/adapters/sqlite/gommon_generated.go
ice/db/adapters/postgres/gommon_generated.go
ice/db/adapters/postgres/adapter.go
ice/db/adapters/postgres/pkg.go
... and 14 more

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