Fixes #72: Require Composer API ^1.1.

[grasmash]

No description provided.

[webflo]

I think this won't fix #72. The plugin version has changed in composer/composer@aeafe2f and the following versions contain this fix.

1.6.4 1.6.3 1.6.2 1.6.1 1.6.0 1.6.0-RC 1.5.6 1.5.5 1.5.4 1.5.3 1.5.2 1.5.1 1.5.0 1.4.3 1.4.2 1.4.1 1.4.0 1.3.3 1.3.2 1.3.1 1.3.0 1.3.0-RC 1.2.4 1.2.3 1.2.2 1.2.1 1.2.0 1.2.0-RC 1.1.3 1.1.2 1.1.1 1.1.0 1.1.0-RC

[webflo]

This does not improve anything. I think we can keep as it is.