Attempt to run Julia (nightly) again for coverage numbers

[jiahao]

This PR attempts to close #79 by rerunning Julia nightlies to generate coverage data.

It all seems to work, except that Coverage fails with an inscrutable error:

Coverage.MallocInfo[]
src/algorithms.jl
src/cie_data.jl
src/Color.jl
src/colormaps.jl
src/colormatch.jl
src/colorspaces.jl
src/conversions.jl
src/differences.jl
src/display.jl
src/maps_data.jl
src/names_data.jl
src/parse.jl
src/utilities.jl
ERROR: cfunction: return type of write does not match
 in associate_stream at /home/travis/.julia/v0.4/GnuTLS/src/GnuTLS.jl:299
 in open_stream at /home/travis/.julia/v0.4/Requests/src/Requests.jl:219
 in send_multipart at /home/travis/.julia/v0.4/Requests/src/Requests.jl:515
 in do_request at /home/travis/.julia/v0.4/Requests/src/Requests.jl:562
 in post at /home/travis/.julia/v0.4/Requests/src/Requests.jl:579
 in submit at /home/travis/.julia/v0.4/Coverage/src/Coverage.jl:217
 in process_options at ./client.jl:241
 in _start at ./client.jl:403

I'm not sure what could have changed in the past 4 days between build #116 and build #115 to cause this. And then there's build #118 where printing out the environment apparently circumvents this error. Any ideas @IainNZ ?

[IainNZ]

That looks like the issue fixed by this https://github.com/JuliaWeb/GnuTLS.jl/pull/38 that was tagged here https://github.com/JuliaLang/METADATA.jl/pull/2178

[jiahao]

Inscrutable