Revamp for Julia v0.6

[odow]

This PR should probably be split into some smaller ones

Allowing .sol files to be read from an IO stream

I'm playing around with the NL file-format interface to NEOS (ref https://neos-server.org/neos/solvers/milp:CPLEX/NL.html and jump-dev/NEOSServer.jl#17).

I made some changes so I can read the .sol file from a stream instead of having to write the file to disk.

Changed tests to @testset

I've also removed CoinOptServices from the testing suite as it needs some work and was causing failures on my windows machine.

Dumping the XXXNLSolver

I've removed BonminNLSolver, CouenneNLSolver, and IpoptNLSolver (and therefore the conditional dependencies) in favour of forcing the user to explicitly construct the solvers.

using AmplNLWriter
solver = IpoptNLSolver()

becomes

using AmplNLWriter, Ipopt
solver = AmplNLSolver(Ipopt.amplexe)

which is a bit more clear and less magical about what is actually occuring.

This is a hard breaking change for current users.

Hopefully this fixes #65

Todo before merge

• update README
• update JuMP solver table

Removed support for v0.5

This uses Julia v0.6 syntax (.!) but doesn't change the REQUIRE yet so still todo:

• [ ] fix deprecation properly by bumping version or using compat

Closes #64

Better error message

If a solver crashes without producing a .sol file the user gets a slightly more helpful error message. Closes #67

Added codecov

Closes #69

[mlubin]

Please drop 0.5!

[odow]

I might put some effort into sorting out the tests while I'm at it.

[mlubin]

This is a big breaking change and needs corresponding updates to the README and JuMP's solver table.

[odow]

Yeah I'm not planning on merging this any time soon. Just trying it out. Yay/Nay on whether this is a good idea?

[mlubin]

Go for it. This dependency is very flaky.

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@ddfbc2f). Click here to learn what that means.
The diff coverage is 0%.

@@          Coverage Diff           @@
##             master   #66   +/-   ##
======================================
  Coverage          ?    0%           
======================================
  Files             ?     4           
  Lines             ?   644           
  Branches          ?     0           
======================================
  Hits              ?     0           
  Misses            ?   644           
  Partials          ?     0

Impacted Files	Coverage Δ
src/nl_convert.jl	0% <0%> (ø)
src/AmplNLWriter.jl	0% <0%> (ø)
src/nl_write.jl	0% <0%> (ø)
src/nl_linearity.jl	0% <0%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update ddfbc2f...f93b1b5. Read the comment docs.

[odow]

This is probably ready to be merged.

Once it is merged, I might go through and have another tidy up. Then we should tag a new version in METADATA and merge the JuMP PR to reflect the changes in the solver table.

[odow]

Merging this so that we can make progress with other PRs. Cc @ccoffrin