DVSNI (VA) timeout

[rolandshoemaker]

Fixes #226, this only adds a timeout to the DVSNI dialer since the comment on the HTTP Client struct seems to imply that the set timeout includes TCP connection time etc...

    // Timeout specifies a time limit for requests made by this
    // Client. The timeout includes connection time, any
    // redirects, and reading the response body. The timer remains
    // running after Get, Head, Post, or Do return and will
    // interrupt reading of the Response.Body.

If this isn't the case (I haven't had a chance to test it), we can set a timeout at the TCP level by altering the Transport on L78 to include a custom dialer, as such

Dial: (&net.Dialer{Timeout:   5 * time.Second}).Dial,

[coveralls]

Coverage remained the same at 43.33% when pulling 99d7ed7 on va-timeout into ef5f95d on master.

[jcjones]

Let's make a test for these two timeouts. We can either do that in #226, or in this PR. As-is, I don't want to call something with this potential impact fixed unless we can write a little loopback test.

[rolandshoemaker]

Just about to add a test for this, should be pushed in a bit.

[jcjones]

This is clear to merge when the tests pass.