Add subscript methods to component pool protocol for fix building library on Xcode 9.3

[atom-wintermute]

I tried to build library on Xcode 9.3 beta and received errors:

1) Expected method to read dictionary element not found on object of type 'id' 2) Expected method to write dictionary element not found on object of type 'id'

Adding subscript methods solves this problem.

[codecov-io]

Codecov Report

Merging #584 into master will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #584   +/-   ##
=======================================
  Coverage   90.84%   90.84%           
=======================================
  Files         185      185           
  Lines        6162     6162           
  Branches      389      388    -1     
=======================================
  Hits         5598     5598           
  Misses        561      561           
  Partials        3        3

---

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 ed450cb...eb6baf3. Read the comment docs.

[jasperblues]

Thanks very much @atom-wintermute, do you need a new CocoaPods build?

[atom-wintermute]

@jasperblues, yes, it would be great.

[jasperblues]

👍 done

[atom-wintermute]

Thanks a lot!