Dependency update in README and update ruby versions in travis-ci.

Author: gkellogg

.travis.yml

@@ -4,12 +4,12 @@ script: "bundle exec rspec spec"
 env:
   - CI=true
 rvm:
-  - 2.2.4
-  - 2.3.0
-  - jruby-9.0.4.0
-  - rbx-2
+  - 2.2.5
+  - 2.3.1
+  - jruby-9.0.5.0
+  - rbx
 cache: bundler
 sudo: false
 matrix:
   allow_failures:
-      - rvm: rbx-2
+      - rvm: rbx

README.md

@@ -31,8 +31,8 @@ Note that in most cases, if the instance is empty and mutable, the appropriate s
 
 ## Dependencies
 
-* [RDF.rb](http://rubygems.org/gems/rdf) (>= 0.3.1)
-* [RSpec](http://rubygems.org/gems/rspec) (>= 2.1.0)
+* [RDF.rb](http://rubygems.org/gems/rdf) (~> 2.0)
+* [RSpec](http://rubygems.org/gems/rspec) (~> 3.0)
 
 ## Installation