port parquet source from twitter
make users to specify fields for ParquetTupleSource explicitly
fix bug: should be able to specify mutiple paths to
FixedPathParquetThrift; fix author name
multiple paths for ParquetTuple source, add companion object to construct tuple source, format
Add semi-general support for scalding modules within scald.rb.

Add --<short-module-name> (i.e. without leading scalding) to
scald.rb command line to include the related module jar to
the build and local run command lines.

Finally, add a new Json example which makes use of the new support.

Note that an extra copy of jackson is in hadoop jar thus
promote all scalding core and module jars to the front of
the generated CLASSPATH to ensure that the good copy
in avro jar is found first.
Merge pull request #776 from tsdeng/parquet_source

port parquet source from twitter
Merge pull request #782 from ljrittle/module-support-in-scald.rb

Add semi-general support for scalding modules within scald.rb.
Merge branch 'develop' of https://github.com/twitter/scalding into develop