Remove unused let-binding
Update the installation instructions

cl-cffi-gtk has to be downloaded from quicklisp. The repo in the README is outdated.
README: fix typo
Merge pull request #52 from joachifm/typo

README: fix typo
Merge pull request #50 from joachifm/unused-binding

Remove unused let-binding
Merge pull request #51 from Ralt/patch-1

Update the installation instructions
Add travis-ci support

Currently, the script only tests whether the
package loads successfully.