Nest default formats and properly merge specified formats
Nest default formats and properly merge specified formats

Closes #49

jeffvan576/intl-messageformat,yahoo/intl-messageformat,mattikl/intl-messageformat,jeffvan576/intl-messageformat,yahoo/intl-messageformat,rlivsey/intl-messageformat,mattikl/intl-messageformat,yahoo/intl-messageformat,ericf/intl-messageformat,ericf/intl-messageformat,jeffvan576/intl-messageformat,rlivsey/intl-messageformat,rlivsey/intl-messageformat,ericf/intl-messageformat,mattikl/intl-messageformat