Add Travis CI support, using SBCL 64 bit.

1. Add travis CI config tweaked from cl-travis.
2. Exclude travis CI config from git ignore list.
3. Add travis logo to README.
4. Add system test operation in a new test file.
5. Add the new test file to system definition.

Initially only ncore package is tested. Other package tests and more lisps to
be added.
Merge pull request #14 from dmsurti/travis-integration

Add Travis CI support, using SBCL 64 bit.