Fixed Ruby conformance tests by running them under rvm Ruby.

ruby/Gemfile.lock

 PATH
   remote: .
   specs:
-    google-protobuf (3.0.0.alpha.5.0)
+    google-protobuf (3.0.0.alpha.4.0)
 
 GEM
   remote: https://rubygems.org/

ruby/ext/google/protobuf_c/defs.c

@@ -543,8 +543,7 @@ VALUE FieldDescriptor_name_set(VALUE _self, VALUE str) {
 
 upb_fieldtype_t ruby_to_fieldtype(VALUE type) {
   if (TYPE(type) != T_SYMBOL) {
-    rb_raise(rb_eArgError, "Expected symbol for field type, not: %s (%d)",
-             RSTRING_PTR(rb_inspect(type)), TYPE(type));
+    rb_raise(rb_eArgError, "Expected symbol for field type.");
   }
 
 #define CONVERT(upb, ruby)                                           \

ruby/travis-test.sh

@@ -17,8 +17,8 @@ test_version() {
       "rvm install $version && rvm use $version && \
        which ruby && \
        gem install bundler && bundle && \
-       rake test"
-    cd ../conformance && make test_ruby
+       rake test &&
+       cd ../conformance && make test_ruby"
   fi
 }