Remove jeweler.

Thus reversing the role of gemspec and Gemfile. So we can run bundle exec
bin/sequenceserver during development again (crucial to this functionality
is calling `gemspec` in Gemfile).

Gone with jeweler are unnecessary dependencies some of which still work on Ruby
1.8.7 and some that don't (yes, we need to support 1.8.7 as long as it takes).

Signed-off-by: Anurag Priyam <anurag08priyam@gmail.com>