Updated tests for full coverage

Code in package registration wrapper is not tested for coverage due to environment constraints. Test results reflect that, but coverage is 100%.

```
[17:19][apipkin:~/Projects/intl-messageformat(tests)]$ npm test

> intl-messageformat@0.0.1 pretest /Users/apipkin/Projects/intl-messageformat
> grunt jshint

Running "jshint:all" (jshint) task
>> 2 files lint free.

Done, without errors.

> intl-messageformat@0.0.1 test /Users/apipkin/Projects/intl-messageformat
> istanbul cover -- _mocha tests/ --reporter spec



  message resolvedOptions
    ✓ empty options

  message creation
    ✓ simple string formatting
    ✓ simple object formatting
    ✓ simple object with post processing tokens
    ✓ complex object formatter
    ✓ complex object formatter with invalid valueName
    ✓ complex object formatter with offset
    ✓ Simple string formatter using a custom formatter for a token
    ✓ Simple string formatter using an inline formatter for a token
    ✓ Simple string formatter using a nonexistent formatter for a token
    ✓ Custom formatters with hidden inheritance
    ✓ broken pattern

  message creation for plurals
    ✓ zero
    ✓ one
    ✓ two
    ✓ few
    ✓ many
    ✓ other


  18 passing (9ms)

=============================================================================
Writing coverage object [/Users/apipkin/Projects/intl-messageformat/coverage/coverage.json]
Writing coverage reports at [/Users/apipkin/Projects/intl-messageformat/coverage]
=============================================================================

=============================== Coverage summary ===============================
Statements   : 98.84% ( 85/86 )
Branches     : 93.06% ( 67/72 )
Functions    : 100% ( 8/8 )
Lines        : 98.84% ( 85/86 )
================================================================================
```