fixes test errors, but tests are still failing

[sbromberger]

The tests are failing with sizes being exactly twice (or half?) what the tests say they should be. An excerpt:

ERROR: LoadError: Generated output differs from cached test output:
pentagon_labeled.svg
pentagon_longarrows.svg
pentagon_noarrows.svg
pentagon_spring.svg
pentagon_stress.svg
random_spring.svg
random_spring_color.svg
random_stress.svg
tree_1.svg
tree_2.svg

pentagon_labeled.svg:
5c5
<      width="101.6mm" height="101.6mm" viewBox="0 0 101.6 101.6"

---
>      width="203.2mm" height="203.2mm" viewBox="0 0 203.2 203.2"
12,71c12,71
<   <path fill="none" d="M18.27,30.27 L 12.64 29.47"/>
<   <path fill="none" d="M16.44,33.7 L 12.64 29.47"/>
<   <path fill="none" d="M93.13,72.43 L 12.64 29.47"/>
<   <path fill="none" d="M39.2,88.14 L 34.73 91.65"/>
...
----
>   <path fill="none" d="M36.53,60.54 L 25.28 58.94"/>
>   <path fill="none" d="M32.87,67.39 L 25.28 58.94"/>
>   <path fill="none" d="M186.27,144.86 L 25.28 58.94"/>
>   <path fill="none" d="M78.39,176.28 L 69.47 183.31"/>
...

[sbromberger]

Also, the dependency on JuMP has changed: instead of loading tree_opt.jl when JuMP is included, the functions in tree_opt.jl are defined ONLY if JuMP is available (and JuMP will be loaded iff it is available).

[hustf]

In draw.jl line 3, ComposeColor now means something counter-intuitive.

typealias ComposeColor Union(Colors.Color, Colors.AlphaColor, Colors.String)

The first two types are the two subtypes of Colors.Colorant. The third type is just a string.
I don't know yet if Compose supports it (it should), but I am tempted to switch to pass the Colors.Colorant type, strings interpreted by the rich functionality in Colors.parse.jl. Default strings could include some weak transparency to show off the functionality.