Add support for Jasmin JVM assembly

[Jasmin](http://jasmin.sourceforge.net) is an assembler for the Java Virtual Machine. It takes ASCII descriptions of Java classes, written in a simple assembler-like syntax using the Java Virtual Machine instruction set. It converts them into binary Java class files, suitable for loading by a Java runtime system. Jasmin is mostly used in education, being used in many compiler classes. 

I've been working with Jasmin a lot for a [compilers project](https://github.com/hawkw/decaf). Jasmin assembly files are usually given the extension `.j`, and I was getting tired of Linguist marking them as Objective-J. In addition to my project, there are [a](https://github.com/metaborg/spoofax-jasmin) [few](https://github.com/travisdazell/Jasmin-Examples) [other](https://github.com/ker2x/MiouLang) [GitHub](https://github.com/travisdazell/Jasmin-HelloWorld) [repos](https://github.com/aminpy/jasmincalc) which also contain Jasmin byte code.

My pull request adds a definition of Jasmin to `languages.yml`, adds a Jasmin TextMate grammar from @atmarksharp's SublimeText [plugin](https://github.com/atmarksharp/jasmin-sublime), and adds a few sample files.