Friendlier build error

Hide the backtrace and show a comprehensible message.

Closes #160.
Stop 'fig up' when a container exits

Closes #1 ヽ(*・ω・)ﾉ
Scaling down removes containers

Squashed version of #162.
Closes #121.
Merge pull request #171 from orchardup/scaling-down-removes-containers

Scaling down removes containers
Updates the mac build script so it wont fail when the venv folder does not exist.
Merge pull request #173 from colinmccune/master

Fixes the mac build script so it wont fail when the venv folder doesn't exist
Merge pull request #165 from orchardup/number-one

Stop 'fig up' when a container exits
Merge pull request #164 from orchardup/friendlier-build-error

Friendlier build error
Improve error message when link does not exist
Merge pull request #180 from orchardup/better-error-message-for-broken-links

Improve error message when link does not exist
Use utf8 when building docs
Add Docker 0.9.0 to Travis