Test script needs to test file writing

[kibaekkim]

The test script should test writing files fro CBF and SDPA formats. The current file write functions are not working, although the commit comment says test passed.
Related to #26

[kibaekkim]

I have reported bugs for both CBF and SDPA writers in MOI.

• Several fixes for SDPA format have already been made and pushed to the master branch and will be ported to 0.9.14.
• I do not see any fix for CBF format yet. It looks like there is a fundamental design flaw in JuMP to support SDP write in CBF format: Incorrect CBF file output jump-dev/MathOptInterface.jl#1072 @bcdandurand: This may be related to Missing function: add_psd_initial_cuts #25?

But, integer variables are not supported in SDPA format. I threw the issue to MOI: jump-dev/MathOptInterface.jl#1074

[bcdandurand]

CBF format is tested in test/runtests.jl as of last push to master.

I haven't looked at what has been done with SDPA format yet, and these are not in test yet, so I'm keeping the issue open.

[kibaekkim]

I have pushed the updated test scripts. I decided to use JuMP functions for writing files. So we don't need to test it in our package.