10 redoc

[dgkf]

Closes #8
Closes #10

• test_examples_as_testthat will now re-roxygenize prior to running tests. Can be disabled by providing roxygenize = FALSE.
• Syntax of different testing strategies has been unified under testex(), with choice of syntax determined by a new argument, style ("testthat", or "standalone"` (default)).
• Similarly, with_srcref is no longer needed within the documentation code, the srcref information is now passed to testex() using the srcref argument, consolidating the interface into a single function call.
• Adds a new config field, "version", which will be injected automatically. It records the version of testex used when writing Rd files (when using roxygen2) and is used to report and handle situations where there is a version mismatch between the version used to write the documentation and execute the tests.