Refactor to include MarcField object with subfield accessors.

Simplifies data access.  Instead of fields() returning an
array of arrays with interleaved subfield names and values,
we return an array of MarcField objects with easier subfield()
and indicator() accessors.  Also adds .html() method, which
outputs a marc field in html, wrapped with classnames for
field, indicator and subfields.
Stash rcns in Field objects at initialization in case they're filtered.
Merge pull request #1 from rych/labor_day

Refactor to simplify access.  Also adds html() method that spits out spanned html from marc.
Allow reordering of subfields in html output.

Also change internal representation of marc json from interleaved
array of subfield label / subfield value to an array of tuples
to allow easier sorting.
Store subfields as objects instead of arrays.
Add mutation and conversion methods.

Also change return values to be compatible with
angularjs's dirty checking.
Merge pull request #2 from rych/reordering

Reordering
Add replace() method for overwriting subfield data.
Add bower config.  Version 0.0.1
Add record type accessor and ctrl field mutation support.
Merge pull request #3 from rych/rtype

Record type and field mutation methods.
Add more field accessors and mutators.
Add MFHD format.
Chop punctuation in title() method.
Add MarcField.del(), MarcField.clone() and MarcRecord.rcn()
Update tests to match api changes.
v1.0.0

Add documentation, README, LICENSE.