new location for doc directory

[brycefisher]

AFAIK, rust-ci is looking for my documentation ./doc/. However, cargo now builds the docs inside the target directory (./target/doc). It would be nice if rust-ci automatically looked in the place cargo uses by default :-)

[tomaka]

It would also be nice if the script automatically called cargo doc (and ignore any error, in case the library doesn't support cargo).

[brycefisher]

@tomaka hmm, I haven't looked at the cargo doc command recently. Are there flags that can be passed to it? I feel like the developer should be responsible to build the docs using whatever process seems right to them. For instance, if you didn't want cargo to run the doc tests but rust-ci forced the doc tests to run, that would be really annoying. I think just looking in the default location is sufficient.