Many code changes to make everything work with Path and XmlInputFormat. Completes milestone 2.

The existing code works with Files. Hadoop works with [Paths](http://hadoop.apache.org/docs/r2.3.0/api/org/apache/hadoop/fs/Path.html) and [FileSystem](http://hadoop.apache.org/docs/r2.3.0/api/org/apache/hadoop/fs/FileSystem.html) which provide an abstraction over files and file systems. That is to say, Hadoop encapsulates the stuff about distributed or local files and files systems and lets us work with Paths and InputFormats. This pretty much sums up most of the stuff in the commits.

Other than that, I added the XmlInputFormat. I tested with run-extraction-test and everything works. DistRedirectsTest passes. I added some docs too.

Please note that I have taken care to make the commits in a specific sequence. If you make your way from commit 4b9745f to commit d08417f it'll be easier to understand what's going on.

Also, it's worth a mention that you'll need to clone https://github.com/nilesh-c/extraction-framework , switch to the **fromxml** branch and run `mvn install` before building this repo on this branch. I've made a PR to extraction-framework with the changes in **fromxml**.
I think the cleanest way would be this: InfoboxExtractor should only produce the subject-property-value dataset (e.g. raw_infobox_properties_en.nt), not the list of all property URIs. That is, remove seenProperties and the whole ```seenProperties.synchronized {...}``` block. After the extraction is done, some kind of script (a few lines of bash / sed / awk would probably do) can go through raw_infobox_properties_en.nt and produce the list of all property URIs, e.g. raw_infobox_property_definitions_en.nt. Running that script probably won't take more than a few minutes per language, so you don't even have to distribute it.