change example extension to .gidl, mention vim and emacs modes in readme

Makefile

@@ -10,7 +10,7 @@ test: rpc-backend-test
 haskell-backend-test:
 	cabal run gidl -- -b haskell \
 		--debug \
-		-i tests/example.idl \
+		-i tests/example.gidl \
 		-o tests/gidl-haskell-backend-test \
 		-p gidl-haskell-backend-test \
 		-n Gidl.Haskell.Test
@@ -24,7 +24,7 @@ haskell-backend-test-clean:
 ivory-backend-test:
 	cabal run gidl -- -b ivory \
 		--debug \
-		-i tests/example.idl \
+		-i tests/example.gidl \
 		-o tests/gidl-ivory-backend-test \
 		-p gidl-ivory-backend-test \
 		-n Gidl.Ivory.Test
@@ -38,7 +38,7 @@ ivory-backend-test-clean:
 tower-backend-test:
 	cabal run gidl -- -b tower \
 		--debug \
-		-i tests/example.idl \
+		-i tests/example.gidl \
 		-o tests/gidl-tower-backend-test \
 		-p gidl-tower-backend-test \
 		-n Gidl.Test
@@ -53,7 +53,7 @@ rpc-backend-test:
 	cabal copy
 	cabal run gidl -- -b haskell-rpc \
 		--debug \
-		-i tests/example.idl \
+		-i tests/example.gidl \
 		-o tests/gidl-rpc-backend-test \
 		-p gidl-rpc-backend-test \
 		-n Gidl.Test

README.md

@@ -7,7 +7,7 @@ describing structured types and RPC-style interfaces.
 
 ## Overview
 
-[Jump right to an example of gidl.](https://github.com/galoisinc/gidl/tree/master/tests/example.idl)
+[Jump right to an example of gidl.](https://github.com/galoisinc/gidl/tree/master/tests/example.gidl)
 
 ### Types
 
@@ -45,7 +45,7 @@ on the wire by a hash of its name, its type, and all child types. Therefore
 ## IDL format
 
 The gidl IDL uses a s-expression based format. The IDL format currently is
-documented in `tests/example.idl`
+documented in `tests/example.gidl`
 
 ## Backends
 
@@ -99,10 +99,21 @@ The default target builds the gidl library. You can then use `cabal run gidl --
 information.
 
 Use the `test` target in the Makefile to generate and test each backend
-implementation. The `tests/example.idl` file is used as the input language.
+implementation. The `tests/example.gidl` file is used as the input language.
 You may then browse generated code for each implementation, which is generated
 and built in subdirectories of the `tests` directory.
 
+## Editor Modes
+
+There is a vim-mode available at [`pchickey/vim-gidl`](https://github.com/pchickey/vim-gidl).
+
+There is an emacs-mode available at [`aisamanra/gidl-mode`](https://github.com/aisamanra/gidl-mode)
+and through an elisp archive at [`http://gelpa.gdritter.com`](http://gelpa.gdritter.com).
+
+If an emacs user uses the emacs package manager, they can just add a line to
+their `.emacs` and then install it either interactively with `M-x package-list`
+or automatically with `(use-package gidl-mode :ensure t)`
+
 ## About
 
 Gidl was created at [Galois][] by Pat Hickey, with help from Getty Ritter and