Support submit from Appveyor

[omus]

The Codecov submit function only works from within Travis CI. I found the note below while getting the Repository Upload Token on Codecov:

Note: Token not required for public repositories uploading from Travis, CircleCI or AppVeyor.

From this comment and from inspecting the codecov-bash source it should definitely be possible to support Appveyor. The relevant Appveyor environmental variables can be found here

[omus]

I tried to make a work around with adding this to my appveyor.yml:

after_test:
  - C:\projects\julia\bin\julia -e "cd(Pkg.dir(\"PKG\")); Pkg.add(\"Coverage\"); using Coverage;
      Codecov.submit(process_folder(),
        service=\"appveyor\",
        branch=ENV[\"APPVEYOR_REPO_BRANCH\"],
        commit=ENV[\"APPVEYOR_REPO_COMMIT\"],
        pull_request=get(ENV, \"APPVEYOR_PULL_REQUEST_NUMBER\", \"\"),
        job=join([ENV[\"APPVEYOR_ACCOUNT_NAME\"], ENV[\"APPVEYOR_PROJECT_SLUG\"], ENV[\"APPVEYOR_BUILD_VERSION\"]], \"%2F\"),
        slug=ENV[\"APPVEYOR_REPO_NAME\"],
        build=ENV[\"APPVEYOR_JOB_ID\"],
      )"

Unfortunately this doesn't work and crashes when trying to evaluate ENV["TRAVIS_BRANCH"]

ERROR: KeyError: TRAVIS_BRANCH not found

[omus]

Trying to use submit_generic as an additional work around.

[omus]

I got the following to submit coverage information on Julia 0.4 (newer Julia versions have an issue):

after_test:
  - C:\projects\julia\bin\julia -e "cd(Pkg.dir(\"PKG\")); Pkg.add(\"Coverage\"); Pkg.add(\"URIParser\"); using Coverage, URIParser;
      Codecov.submit_generic(process_folder(),
        service=\"appveyor\",
        branch=ENV[\"APPVEYOR_REPO_BRANCH\"],
        commit=ENV[\"APPVEYOR_REPO_COMMIT\"],
        pull_request=get(ENV, \"APPVEYOR_PULL_REQUEST_NUMBER\", \"\"),
        job=escape(join([ENV[\"APPVEYOR_ACCOUNT_NAME\"], ENV[\"APPVEYOR_PROJECT_SLUG\"], ENV[\"APPVEYOR_BUILD_VERSION\"]], '/')),
        slug=ENV[\"APPVEYOR_REPO_NAME\"],
        build=escape(ENV[\"APPVEYOR_JOB_ID\"]),
      )"