several fixes

[timotheecour]

/cc @yglukhov @SSPkrolik

• test/document Bson(string) to string
• fixes #54
• fixes #56 EDIT
• fixes pre-existing bug in .travis.yml (was previously not really testing anything)
• add nimble test, nimble test_ci commands to test with or without mongod

[timotheecour]

hmm, indeed, nim c -r nimongo/bsontest is mentioned in .travis.yml and doesn't fail... sounds like a pre-existing bug

[timotheecour]

@SSPkrolik @yglukhov I tested locally (based on output from https://travis-ci.com/timotheecour/nimongo/jobs/159187423) , it turns out travis.yml is buggy, can we please merge this and figure out travis after?

mkdir /tmp/d02 && cd /tmp/d02
git clone --depth=50 --branch=master https://github.com/timotheecour/nimongo.git timotheecour/nimongo
docker pull yglukhov/nim-base

# passes
docker run -v "$(pwd):/project" -w /project yglukhov/nim-base run "nimble install -y && nim c -r nimongo/bson && nim c -r nimongo/bsontest"

# also passes, with random string
docker run -v "$(pwd):/project" -w /project yglukhov/nim-base run "nimble install -y && nim c -r nimongo/bson && nim c -r adfasfjalfjaslfjasdlfjalsjfalsjfasljfalsdfj"

[timotheecour]

@SSPkrolik @yglukhov PTAL, I fixed travis, there was a pre-existing bug (run vs bash); also I adapted travis to run nimble test_ci so we can test both nimble test (locally, if there's a mongod server) vs nimble test_ci

in a future PR, we should make travis run nimble test and add dependency on mongod in travis => https://github.com/SSPkrolik/nimongo/issues/62

[timotheecour]

/cc @yglukhov I added some commits ; lemme know if u want these in another PR

[timotheecour]

ping

[SSPkrolik]

@timotheecour thanks a lot for the contribution!