Add citer-cli

[jwilk]

This adds a command-line interface.
Useful for people like me who despise web interfaces. Might be also useful for debugging.

The code is not pretty, but hey, it works.

Example:

$ ./citer-cli 10.1007/978-1-4302-6713-3_3
{{sfn | Akramullah | 2014 | pp=55–100}}

* {{cite book | last=Akramullah | first=Shahriar | title=Digital Video Concepts, Methods, and Metrics | chapter=Video Coding Standards | publisher=Apress | publication-place=Berkeley, CA | year=2014 | isbn=978-1-4302-6712-6 | doi=10.1007/978-1-4302-6713-3_3}}

<ref name="Akramullah 2014 pp. 55–100">{{cite book | last=Akramullah | first=Shahriar | title=Digital Video Concepts, Methods, and Metrics | chapter=Video Coding Standards | publisher=Apress | publication-place=Berkeley, CA | year=2014 | isbn=978-1-4302-6712-6 | doi=10.1007/978-1-4302-6713-3_3 | pages=55–100}}</ref>