default missing ind1 and ind2 to blank

Should be fully backward compatible.

I am given library data which contains records like

```
<marc:datafield tag="946" ind1=" " ind2=" ">
    <marc:subfield code="a">No</marc:subfield>
  </marc:datafield>
  <marc:datafield tag="949">
    <marc:subfield code="a">Article</marc:subfield>
  </marc:datafield>
```

(missing `ind1` & `ind2` in 949), which makes `map_xml()` parsing fail with `KeyError: (None, u'ind1')`.
Make installation options more clear
Merge pull request #34 from lbjay/master

super minor tweak to make a clear distinction between the two installation options
no longer bundle ez_setup.py and give instructions for downloading setuptools in README.md fixes #35
resolved doc conflict
Merge pull request #33 from piskvorky/patch-1

default missing ind1 and ind2 to blank
allow pymarc.Record subclasses to be written by MARCWriter

* `type` demands equality of types, while `isinstance` caters for inheritance
Added JSONReader and a test case for it
remove print() invocation and future import for better(?) backward compatibility
Merge pull request #37 from adjam/master

Add JSONReader
upped version for release
doc fix
variation on the fix proposed in #41. fixes #41
Merge branch 'master' of github.com:edsu/pymarc
not sure how we lost the test suite in setup.py ...
upped version for release
Added support of shorthand membership testing for records and fields
Merge pull request #43 from DavidChouinard/master

Added support of shorthand membership testing for records and fields
Merge pull request #36 from miku/feature/subclass

allow pymarc.Record subclasses to be written by MARCWriter
upped version for release