Support same versions as http gem

(see httprb/http#390)

Author: abotalov

.travis.yml

@@ -4,19 +4,12 @@ env:
     - JRUBY_OPTS="$JRUBY_OPTS --debug"
 language: ruby
 rvm:
+  - jruby-9.1.7.0
+  - 2.0.0
   - 2.1
   - 2.2
-  - 2.3.0
-  - 2.3.1
-  - 2.3.2
   - 2.3.3
   - 2.4.0
-  - ruby-head
-  - jruby-9.1.6.0
-  - jruby-head
 matrix:
-  allow_failures:
-    - rvm: ruby-head
-    - rvm: jruby-head
   fast_finish: true
 sudo: false

README.md

@@ -62,7 +62,7 @@ versions:
 * Ruby 2.2.x
 * Ruby 2.3.x
 * Ruby 2.4.x
-* JRuby 9.1.6.0
+* JRuby 9.1.x.x
 
 If something doesn't work on one of these versions, it's a bug.