requirements.txt: Add pyjsparser
requirements.txt: Add pyjsparser

Adds requirement pyjsparser for parsing JS files
like "Gruntfile.js"

Related to https://github.com/coala/coala-quickstart/issues/42

coala-analyzer/coala-quickstart,MalkmusT/coala-quickstart,coala-analyzer/coala-quickstart,MalkmusT/coala-quickstart