Add common VHDL file extensions
language interpreters and shebang lines

Add an interpreter array to each language, and match interpreters found
in the shebang lines of scripts to this array to identify the language
of scripts.

With suggestions from tnm. https://github.com/github/linguist/pull/687
adding interpreter arrays to some languages
unit test for find_by_shebang
Adding support for the Brightscript language, with samples.
use JSON instead of YAML for loading samples.json
prefer JSON, but fall back to YAML if JSON isn't available
Merge pull request #806 from github/use-json-for-loading-samples

Use JSON instead of YAML for loading samples.json
require escape_utils >= 0.3.1
force escape_utils 0.3.2 on ruby < 1.9.3
Merge pull request #807 from github/update-escape_utils-dep

Require escape_utils >= 0.3.1
Bump pygments.rb to 0.5.4
2.9.9
prefer to load from languages.json if it exists
Merge pull request #809 from github/languages.json

Prefer to load from languages.json if it exists
Merge pull request #810 from github/bump-pygments

Bump pygments
2.10.0
Colors for agda and tex
Updated the DM language to use the C++ lexer.
Merge pull request #812 from Giacom/patch-1

Updated the DM language to use the C++ lexer.