Removed test/ and static/ directories

The code being tested in test/ is deprecated, old and unmaintained. We should
clean this mess before inviting people to contribute to SciRuby.

The static/ directory contained only a logo, which I will send as a PR to the
sciruby.com source branch.

And, finally, I removed some things from the gemspec -- too many things there.
Improved the README, added CONTRIBUTING.md file

I made changes to the README similar to those made in NMatrix's:

- Re-arranged the headers (all in lowercase).
- Put all the information regarding developers in CONTRIBUTING.md (so it'll
appear when someone opens a pull request).
- Fixed link to the pledgie image.
- Improved link names and descriptions.
- Added link to installation page on the wiki.
- Warned about NMatrix/rb-gsl incompatibility.

Also, explained a little bit about how SciRuby and its subprojects are related
in the CONTRIBUTING.md file.
Removed deprecated options from .rspec

These changes aren't valid as of RSpec 2.3!
Added static/, fixed load path in sciruby-plotter

Reverted the removal of the static/ directory as said in the PR.

The change in bin/sciruby-plotter is necessary for the script to require the
"local" sciruby gem, not the one installed on the system. This way, you can
make changes to your local copy and test then without conflicts with the one
installed, etc.

I didn't add specs because I don't really know how to test a GUI program.
Merge pull request #27 from agarie/cleaning

Cleaning the repo