Ruby 1.8.7 compatibility

[donaldali]

The gemspec file indicates compatibility from ruby 1.8.7 while travis.yml sets up testing from ruby 1.9.3. If compatibility is supposed to be from ruby 1.8.7, then this line breaks that compatibility by using the ruby 1.9 hash syntax.

[liufengyun]

Yes, 1.8.7 is not supported also for some other issue about some ordering change in testing. I forgot to update the gemspec file.

[krzysiek1507]

Minimum Ruby 2.0 is required.