Fix limits on acceptable dependency versions

This version of guard-jruby-rspec is not compatible with guard-rspec
4.x, which depends on guard >= 2.0.

It also lost compatibility with guard-rspec < 2.0.0 in
5f8ec60.

guard-jruby-rspec.gemspec

@@ -15,11 +15,10 @@ Gem::Specification.new do |s|
   s.required_rubygems_version = '>= 1.3.6'
   s.rubyforge_project         = 'guard-jruby-rspec'
 
-  s.add_dependency 'guard', '>= 0.10.0'
-  s.add_dependency 'guard-rspec', '>= 0.7.3'
-
-  s.add_development_dependency 'rspec',   '~> 2.7'
+  s.add_dependency 'guard', '>= 0.10.0', '< 2.0.0'
+  s.add_dependency 'guard-rspec', '>= 2.0.0', '< 4.0.0'
+  s.add_dependency 'rspec', '~> 2.7', '< 2.99'
 
   s.files        = Dir.glob('{lib}/**/*') + %w[LICENSE README.md]
   s.require_path = 'lib'
-end
+end