Add hbs alias for Handlebars

Adds a `hbs` alias for `Handlebars`. It's very commonly used and would make adding hbs code blocks easier in github comments.
Update indenentation
Add .a51 to Assembly

.a51 doc is 8051-asm (coding in MIDE-51)
Add .a51 sample
Merge pull request #1613 from hearsilent/patch-1

Add .a51 to Assembly
Merge pull request #1612 from briandela/patch-1

Add hbs alias for Handlebars
Add a multitude of Forth file extensions.
Yes, these are all in use.
Make test_pedantic accept quotes around extensions.