Parse the chunk options as a set of Julia expressions and store options ...

...in a Dict{Symbol,Any}

This version is okay on `examples/julia_sample.mdw` but on `examples/winston_sample.mdw` produces
```jl
optionstring = "term=true"
options = Dict{Symbol,Any}(:term=>true,:name=>nothing)
optionstring = ""
options = Dict{Symbol,Any}(:name=>nothing)
optionstring = "echo=false; caption=\"Random walk.\"; label=\"random\""
options = Dict{Symbol,Any}(:echo=>false,:label=>"random",:name=>"random",:caption=>"Random walk.")
INFO: Weaving chunk 1 from line 18


WARNING: deprecated syntax "{a=>b, ...}".
Use "Dict{Any,Any}(a=>b, ...)" instead.
INFO: Weaving chunk 2 from line 28

figures/winston_sample_nothing_1.png
ERROR: key not found: :page_margin
 in getindex at ./dict.jl:640
 in getattr at /home/bates/.julia/v0.4/Winston/src/Winston.jl:1056
 in page_compose at /home/bates/.julia/v0.4/Winston/src/Winston.jl:1782
 in savepng at /home/bates/.julia/v0.4/Winston/src/Winston.jl:1844
 in savefig at /home/bates/.julia/v0.4/Winston/src/Winston.jl:1854
 in savefig at /home/bates/.julia/v0.4/Winston/src/plot.jl:14
 in savefigs_winston at /home/bates/.julia/v0.4/JuliaReport/src/JuliaReport.jl:187
 in savefigs at /home/bates/.julia/v0.4/JuliaReport/src/JuliaReport.jl:144
 in run at /home/bates/.julia/v0.4/JuliaReport/src/JuliaReport.jl:133
 in weave at /home/bates/.julia/v0.4/JuliaReport/src/JuliaReport.jl:58
```
but I don't know enough about the Winston device to be able to debug that.

I left some calls to the `@show` macro in the sources.  That is the preferred way of producing debugging output.