add builder dependency to assist in bundling

Bundler was getting confused trying to resolve the builder dependency,
so we specify a dependency even though there is no direct dependency.
This can be removed when the issue is fixed in bundler or if we no
longer depend on any other gems that depend on builder.
set upper bound on rails dependency
set upper bound on nokogiri dependency
set upper bound on cucumber dependency
set upper bound on capybara dependency
consistently use >= for development dependencies
change order of gemfiles for faster builds
cleanup trailing whitespace
Merge pull request #265 from sferik/cleanup2

Additional gemspec cleanup