fix: Use set environment in commands

[jroehl]

Summary

Fix for #68
Find and add management-token, space-id, environment-id and host to context.

Description

Added middleware function (using yargs middlewares) to build the context by checking if the management-token, space-id, environment-id and host are set in the .contentfulrc.json or passed into the command via flags.

Motivation and Context

This fixes #68 and simplifies checking for cli settings.

Todos

• Implemented feature
• Fix tests

[codecov]

Codecov Report

Merging #150 into master will increase coverage by 0.23%.
The diff coverage is 93.67%.

@@            Coverage Diff             @@
##           master     #150      +/-   ##
==========================================
+ Coverage   82.34%   82.58%   +0.23%     
==========================================
  Files          57       57              
  Lines        1144     1131      -13     
==========================================
- Hits          942      934       -8     
+ Misses        202      197       -5

Impacted Files	Coverage Δ
lib/cmds/config_cmds/add.js	84.61% <ø> (+4.61%)	⬆️
lib/context.js	96.77% <ø> (ø)	⬆️
lib/cmds/space_cmds/seed.js	15.38% <0%> (+0.56%)	⬆️
lib/cmds/guide.js	67.64% <0%> (ø)	⬆️
lib/guide/step-seed.js	100% <100%> (ø)	⬆️
lib/cmds/space_cmds/accesstoken_cmds/create.js	95.23% <100%> (ø)	⬆️
lib/cmds/boilerplate.js	95.34% <100%> (+0.11%)	⬆️
lib/utils/assertions.js	100% <100%> (ø)	⬆️
lib/guide/step-login.js	100% <100%> (ø)	⬆️
lib/cmds/space_cmds/import.js	80% <100%> (-4.22%)	⬇️
... and 24 more

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[Khaledgarbaya]

First Round, this looks really great. I have some small comments

[phoebeschmidt]

wow so many files changed 👏 looks good!

CI is just timing out on unit tests but looks like everything is passing

[Khaledgarbaya]

👏 This 👏 is 👏 amazing 👏
One last tiny comment

[Khaledgarbaya]

👏
Can you squash and merge? with a commit message like
feat(context): Use middleware to fill context, the feat part will make sure that the ci will increase the version and release a new version