Reduce the support matrix

Require Node v4, Chai v4, and Sinon v4 at least.

.travis.yml

@@ -1,30 +1,11 @@
 language: node_js
 node_js:
-  - "0.10"
+  - 4
   - stable
 env:
-  # Can't figure out how to DRY this up: http://stackoverflow.com/q/22397300/3191
-  - CHAI_VERSION=^1.9.2 SINON_VERSION=^1.4.0
-  - CHAI_VERSION=^2.0.0 SINON_VERSION=^1.4.0
-  - CHAI_VERSION=^3.0.0 SINON_VERSION=^1.4.0
-  - CHAI_VERSION=^4.0.0 SINON_VERSION=^1.4.0
-  - CHAI_VERSION=^1.9.2 SINON_VERSION=^2.1.0
-  - CHAI_VERSION=^2.0.0 SINON_VERSION=^2.1.0
-  - CHAI_VERSION=^3.0.0 SINON_VERSION=^2.1.0
-  - CHAI_VERSION=^4.0.0 SINON_VERSION=^2.1.0
-  - CHAI_VERSION=^1.9.2 SINON_VERSION=^3.0.0
-  - CHAI_VERSION=^2.0.0 SINON_VERSION=^3.0.0
-  - CHAI_VERSION=^3.0.0 SINON_VERSION=^3.0.0
-  - CHAI_VERSION=^4.0.0 SINON_VERSION=^3.0.0
-  - CHAI_VERSION=^1.9.2 SINON_VERSION=^4.0.0
-  - CHAI_VERSION=^2.0.0 SINON_VERSION=^4.0.0
-  - CHAI_VERSION=^3.0.0 SINON_VERSION=^4.0.0
+  # This matrix used to be larger. In 3.0.0 we moved to only supporting these versions.
+  # But, we'll retain the infrastructure for a larger matrix, in case we need it in the future.
   - CHAI_VERSION=^4.0.0 SINON_VERSION=^4.0.0
 script:
-  - test $TRAVIS_NODE_VERSION == "0.10" || npm run lint
+  - npm run lint
   - npm run test-travis
-before_install:
-  - if [ `npm -v` = "5.3.0" ]; then
-      npm install -g npm@^5.4.2;
-      npm -v;
-    fi

package.json

@@ -28,8 +28,8 @@
     "cover": "istanbul cover node_modules/mocha/bin/_mocha && opener ./coverage/lcov-report/lib/sinon-chai.js.html"
   },
   "peerDependencies": {
-    "chai": ">=1.9.2 <5",
-    "sinon": "^1.4.0 || ^2.1.0 || ^3.0.0 || ^4.0.0"
+    "chai": "^4.0.0",
+    "sinon": "^4.0.0"
   },
   "devDependencies": {
     "chai": "^4.1.0",