docker:doctor needs to allow for slow internet

[kierenevans]

$ dock-cli docker:doctor
Running Docker Doctor
Docker is installed
Docker daemon is running
- Can't ping docker virtual interface., attempting to fix that!
RUN brew --version
OUT Homebrew 0.9.5 (git revision 2d6cd; last commit 2016-02-02)
"homebrew" is already installed
RUN brew cask --version
OUT 0.60.0 (git revision b312b; last commit 2 days ago)
"brewCask" is already installed
 Checking PHP SSH2 extension
PHP SSH2 extension is required.
Which homebrew package do you want to install (default "php56-ssh2") ? ("n" for nothing)
RUN brew install --dry-run php56-ssh2
OUT ==> Installing php56-ssh2 from homebrew/php
OUT ==> Installing dependencies for homebrew/php/php56-ssh2: libpng, freetype, gettext, php56, libssh2
OUT ==> Installing homebrew/php/php56-ssh2 dependency: libpng
OUT ==> Downloading https://homebrew.bintray.com/bottles/libpng-1.6.21.yosemite.bottle.tar.gz
OUT ==> Pouring libpng-1.6.21.yosemite.bottle.tar.gz
OUT 🍺  /usr/local/Cellar/libpng/1.6.21: 17 files, 1.2M
OUT ==> Installing homebrew/php/php56-ssh2 dependency: freetype
OUT ==> Downloading https://homebrew.bintray.com/bottles/freetype-2.6.2.yosemite.bottle.tar.gz
OUT ==> Pouring freetype-2.6.2.yosemite.bottle.tar.gz
OUT 🍺  /usr/local/Cellar/freetype/2.6.2: 60 files, 2.4M
OUT ==> Installing homebrew/php/php56-ssh2 dependency: gettext
OUT ==> Downloading https://homebrew.bintray.com/bottles/gettext-0.19.7.yosemite.bottle.tar.gz



  [Symfony\Component\Process\Exception\ProcessTimedOutException]
  The process "brew install --dry-run php56-ssh2" exceeded the timeout of 60 seconds.



docker:doctor [--dry-run]```

[sroze]

Thank you for reporting. Happy to merge a PR 😃