adds authenticated transport and non-standard api path connections

[bonedaddy]

This PR adds the ability to use go-ipfs-http-client with an endpoint expecting authorization, ie via JWT's. Additionally, it allows connection go-ipfs-http-client to an endpoint that may not be using a standard path, ie /foo/bar/api/v0 as opposed to /api/v0.

Currently multiaddr doesn't support parsing of http paths, which is what NewDirectAPIClient works around. Initially I thought NewApiWithClient might be usable instead, however since it expects a multiaddr and the multiaddr spec doesn't currently support parsing of http paths, this is needed.

edit: Not quite sure why the travis build is failing, but it seems to be some kind of go version check when this part of the build runs (cd $GOPATH/src/github.com/ipfs/go-ipfs; make install)

[magik6k]

Few minor nits, looks good in general, Thanks!

[bonedaddy]

Not quite sure why this error is happening however I've traced the line of code causing it to

go-ipfs-http-client/response.go

Line 113 in 2b48dd3

contentType, _, err := mime.ParseMediaType(resp.Header.Get("Content-Type"))

update: Actually I was being a bit dump, the reason why its happening with this test, is because the test server isn't setting Content-Type header in the response. Additionally the conditional to check the header was improperly specified.

[magik6k]

LGTM, but I'll let @Stebalien have one last look

[bonedaddy]

I believe I forgot to commit removal of the file transport.go, currently out of the house but can commit that when I get back home.

edit: I have pushed a commit to remove the transport.go file.

[magik6k]

@Stebalien lgtm-ed on IRC