Tracking for read transaction parallelization and reads in read transaction

[brettz9]

With our using node-websql under the hood, I wanted to add tracking here for:

• the performance issue mentioned in Read transactions in parallel nolanlawson/node-websql#17 , namely, of ensuring parallelization of read transactions (without causing writer starvation in the process)
• using a read transaction as needed for read operations.

Both issues relate to Node only.

[brettz9]

This might be done with #296

[brettz9]

Tracking this issue on new project at #7