Documented all valid keys for get_global()

[mxsasha]

This adds a simple list of all valid keys for get_global() to the documentation. I've already included the territory_languages key, which is introduced in PR #122.

[sils]

@erikr rebase should also fix the tests

[sils]

also can you use imperative present tense for commit shortlog? Minor nitpick because you seem to have several PRs waiting for review.

[codecov-io]

Current coverage is 83.38%

Merging #123 into master will not affect coverage as of 3405b4f

@@            master    #123   diff @@
======================================
  Files           22      22       
  Stmts         3756    3756       
  Branches         0       0       
  Methods          0       0       
======================================
  Hit           3132    3132       
  Partial          0       0       
  Missed         624     624       

Review entire Coverage Diff as of 3405b4f

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[etanol]

@erikr Why did you create a new PR instead of committing this on top of #122 ?

[akx]

This was closed via #315.