Require Node.js >= 0.10.0

Travis CI builds with Node.js 0.8.x started to fail:

  https://travis-ci.org/dmajda/pegjs/jobs/26691570

Rather than investigating what's wrong I decided to stop supporting Node
0.8.x. Node.js 0.10.x is here for over a year, which should be enough
time for everyone to upgrade in the fast-paced Node.js world.

.travis.yml

@@ -1,4 +1,3 @@
 language: node_js
 node_js:
-  - 0.8
   - 0.10

README.md

@@ -416,7 +416,7 @@ Compatibility
 Both the parser generator and generated parsers should run well in the following
 environments:
 
-  * Node.js 0.8.0+
+  * Node.js 0.10.0+
   * IE 8+
   * Firefox
   * Chrome

package.json

@@ -51,6 +51,6 @@
     "jshint":       "= 2.3.0"
   },
   "engines":         {
-    "node": ">= 0.8"
+    "node": ">= 0.10.0"
   }
 }