cleanup: more comments at top of terminal class

	modified:   src/antsy/terminal.rb
cleanup: replace bunch-o-methods with missing_method method

For all the terminal methods which just print escape codes:
instead store codes in a hash, and use one method (missing_method)
to do the printing.

	modified:   src/antsy/terminal.rb
Added R syntax coloring.

	modified:   src/editor.rb
	modified:   src/syntaxcolors.rb
Updated readme to talk more about philosophy/requirements

	modified:   README.md
Added install option in README (apt-get)

	modified:   README.md