Installation errors if current directory contains a space

When running ./build.sh in a directory containing a space, I get the following output:

``` bash
$ ./build.sh [22:29:38]
/Users/andrew/Desktop/space test/multirust/src/rust-installer/gen-install-script.sh: line 213: cd: /Users/andrew/Desktop/space: No such file or directory
cat: /rust-installer-version: No such file or directory
cat: /install-template.sh: No such file or directory
```

To be clear, the steps to replicate are:

``` bash
mkdir "~/Desktop/space test"
cd ~/Desktop/space\ test
git clone --recursive https://github.com/brson/multirust && cd multirust
git submodule update --init
./build.sh
```

This may be a low priority edge-case, but I thought I'd bring it up anyways. Thanks!