Encode true as xFF

According to the spec: http://tools.ietf.org/html/rfc4511#section-5.1
Force encoding to ASCII-8BIT

We allow this since the library requires Ruby 1.9+
remove rubygems_version

this will be set by the actual version that builds it
http://guides.rubygems.org/specification-reference/#rubygemsversion
requirement does not actually limit anything
use a string for required_ruby_version

See http://guides.rubygems.org/specification-reference/#required_ruby_version
simplify how development dependencies are declared

follows the spec reference defined in http://guides.rubygems.org/specification-reference/
add contributing guide
Merge branch 'master' into true-ber
Merge pull request #146 from ruby-ldap/gemspec-cleanup

Gemspec cleanup
Add BER integration test for true value
changes for 0.9.0
Merge pull request #142 from ruby-ldap/true-ber

Encode true as xFF
fix urls
clarify gem version
Merge pull request #147 from ruby-ldap/add-contributing

Add contributing guide
make bug fixes language consistent
add clean-up section
specify >= 1.9.3 required
Merge pull request #149 from ruby-ldap/0.9.0-changelog-draft

Add changes for 0.9.0 for History.rdoc
alpa sort capability attributes list