Use subject(:gemspec) in favor of instance variables
Change suffix from _rspec to _spec
Drop unnecessary instance variable
Add testing exception message
Improve testing if last error was raised by Bundler::Retry
Clean up context of "determining gemspec"
Refactor specs for Bundler::GemHelper.install_tasks
Refactor specs for Bundler::GemHelper.build_gem
Refactor specs for Bundler::GemHelper.install_gem
Split subject between main contexts
Refactor specs for Bundler::GemHelper.release_gem
Improve using subject in  tests for Bundler.load_gemspec_uncached
Small improving of tests

- Remove unused variables
- Improve specs descriptions
- Simplify some specs scenarios
- Add testing messages while expecting exceptions
Use expect instead of should
Merge pull request #2831 from kiela/clean_up_specs

Clean up specs located in spec/bundler