Add jsonpath.py script that can be used when installing this package

This script is based on https://github.com/makefu/jsonpath but expanded to work well with batches of files, globbing etc.

It will be installed as a bin/ script, so pip installing this package also gives a useful tool for testing and doing stuff. This is really useful, and I had a hard time finding a working JSONpath script (there are so many outdated, or for old versions of perl and what not).

There are two modes: stdin input and file path input

Examples:

```
$ echo '{ "foobar": 1 }' | jsonpath.py foobar
1
```

```
$ jsonpath.py $..myelement *.json
lots of output
here
for every myelement
...
```

Please merge! :)