SystemVerilog language support in Atom

Adds syntax highlighting and snippets to SystemVerilog files in Atom.

This an update to Razer6's language-verilog, originally done in order to have Atom make the distinction between Verilog and SystemVerilog (thereby avoiding linter complaints about non-Verilog code and adding some bits to the script package that'll allow me to run Verilog and SV files differently).

It's been updated according to jfrogget's clone and the other outstanding pull requests.