Updating CONTRIBUTING.md as per Hydra v6.0.0

[ci skip]
Updating README to use markdown and nice badges
bump to 3.0.4
remove README.textile from the gemspec
Updating solrizer, correcting rspec deprecations
Dynamic nodes should implement respond_to? for all values of the target
Raise a type mismatch if a time can't be serialized
Merge pull request #49 from projecthydra/dynamic_respond_to

Dynamic nodes should implement respond_to? for all values of the target
Dynamic nodes should be able to test inequality (!=)
Merge pull request #51 from projecthydra/inequality_not_assignment

Dynamic nodes should be able to test inequality (!=)
Merge pull request #50 from projecthydra/type_mismatch_error

Raise a type mismatch if a time can't be serialized
Bump version to 3.0.5
Merge pull request #47 from projecthydra/solrizer_update

Updating solrizer, correcting rspec deprecations
Bump version to 3.1.0.alpha
Handle invalid time for Rails 3
Setting values on a proxy term should build the parent terms if they don't exist
Merge pull request #53 from projecthydra/proxy_should_build_node

Setting values on a proxy term should build the parent terms
Adding failing test