Bunch O changes

Four commits that I accumulated over time to use Blimpy for our purposes.

Out of my laziness I'm creating a single pull request for these four commits. If you want to strike down some but willing to take others, please let me know so that I can create a pull request accordingly.

#### Forcing ssh_wait is considered harmful
Various blimpy commands silently wait for SSHD to come online on the remote VM, but if there's any misconfiguration in Blimpfile, this will ends up hanging forever (and users will have no clue why.) I think it's better not to do this out of the box. For interactive use, waiting and rerunning the command is easy, and for a scripted use, I added another command `wait_for_ssh` that does it.

#### ssh_info method using ARGV is harmful
`Box` needs to be usable as a library, so its `ssh_into` method looking at `ARGV` is problematic if I'm writing another command or other ruby code that talks to Blimpy. Leave it to the CLI ssh command to look at ARGV.

#### Blimprc file for defining custom commands
I want to write a pseudo-plugin that extends Blimpy with some project specific commands. For that I allowed `Blimprc` in the project directory that gets loaded into Ruby.

#### Minor output improvements
Got rid of annoing empty line.