Added PigLatin language identification.

Updated languages.yml to associate *.pig files with PigLatin.
Added pig script example to samples/.
Updated the samples.json with to account for new sample.

In-the-wild examples on GitHub:
https://github.com/packetloop/packetpig/tree/master/pig
https://github.com/jt6211/accumulo-pig

Can provide more if necessary. Popular language in "big data" field.