`MutableCloneableVector` -> `MutableCloneableSlice`

I don't know much about Rust (yet?), but I just tried to build this and got an
error about `MutableCloneableVector` not existing in `std::slice`. Looks like it
was renamed in 0.12.0 to `MutableCloneableSlice` (rust-lang/rust@4f5b692).
Update `.travis.yml` on new path to `lib.rs`
Merge pull request #2 from KenanY/fix-travis

Update `.travis.yml` on new path to `lib.rs`
Merge pull request #1 from KenanY/mutable-cloneable-slice

`MutableCloneableVector` -> `MutableCloneableSlice`
fix compile error
use cargo build
fix compile error; update README; add .gitignore