Updating docs/README.md

[Musse]

This issue is a follow up to Issue #24

Currently this is a straight port from developerWorks.

I'm creating this issue to list what I think should be updated & for others to also make suggestions.

Examples

1. replace require('/QOpenSys/QIBM/ProdData/OPS/Node4/os400/db2i/lib/db2a') with require('idb-connector')

2. replace var declarations with let and const as appropriate.

3. use single quotes instead of double quotes

4. Remove concurrent query example - documented here that this can be bad!

#Docs

1. update execute() syntax to show execute(out, error)

2. Some of the methods have duplicates for their syntaxes:

For example:

prepare(string SQL, function Callback())

prepare(string SQL, function Callback(Error))

Would change to only show: prepare(string SQL, function Callback(Error)).

[Musse]

resolved in PR #10