Use Rake 12.3 for testing to support Ruby 2.0 and 2.1

Also add JRuby 9.2 as optional in Travis

Author: HarlemSquirrel

.travis.yml

@@ -11,6 +11,7 @@ rvm:
   # optional
   - ruby-head
   - jruby-19mode
+  - jruby-9.2
   - jruby-head
   - rbx-2
 
@@ -48,6 +49,7 @@ matrix:
   allow_failures:
     - rvm: ruby-head
     - rvm: jruby-19mode
+    - rvm: jruby-9.2
     - rvm: jruby-head
     - rvm: rbx-2
   fast_finish: true

net-ldap.gemspec

@@ -26,11 +26,11 @@ the most recent LDAP RFCs (4510-4519, plutions of 4520-4532).}
   s.homepage = %q{https://github.com/ruby-ldap/ruby-net-ldap}
   s.rdoc_options = ["--main", "README.rdoc"]
   s.require_paths = ["lib"]
-  s.required_ruby_version = ">= 2.0.0"
+  s.required_ruby_version = ">= 2.2.0"
   s.summary = %q{Net::LDAP for Ruby (also called net-ldap) implements client access for the Lightweight Directory Access Protocol (LDAP), an IETF standard protocol for accessing distributed directory services}
 
   s.add_development_dependency("flexmock", "~> 1.3")
-  s.add_development_dependency("rake", "~> 13.0")
+  s.add_development_dependency("rake", "~> 12.3")
   s.add_development_dependency("rubocop", "~> 0.49.0")
   s.add_development_dependency("test-unit")
   s.add_development_dependency("byebug")