Character order and measurement systems

[akx]

This is a fixed version of @alexbodn 's PR #367.

The get_unit_name API from that PR is intentionally excluded; a format_unit API will be included in a subsequent PR.

[codecov-io]

Current coverage is 89.11%

Merging #368 into master will decrease coverage by -0.64% as of 01c62dc

@@            master    #368   diff @@
======================================
  Files           23      23       
  Stmts         3854    3860     +6
  Branches         0       0       
  Methods          0       0       
======================================
- Hit           3459    3440    -19
  Partial          0       0       
- Missed         395     420    +25

Review entire Coverage Diff as of 01c62dc

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[alexbodn]

thank you very much @akx .
the international web sites developers,
and the pint measurement units project
will enjoy these enhancements the moment you will pull them.

if you could, please tell me when to tell pint people to use upstream instead of my babel.

[jtwang]

This would have been a great use of a Python 3.4 Enum. Just an observation, no need to do anything here. :)

[akx]

Assigned @jtwang for having done initial review on this.

[akx]

Disregard the Codecov fail, btw. I think it's being confused again...

[jtwang]

@akx - OK to merge! Just the nit about two methods, ignore if you want. ;)

[akx]

Nits acknowledged.

[akx]

Gah, this PR shows up in my list of open PRs even if it's merged.

EDIT: Welp, adding this comment fixed the issue.