multiverse 0.6.2

Added functions to allow export of the multiverse results as JSON to be compatible with Milliways. EMARs are not yet supported however, as that requires changes to knitr
Added support for naming variables when extracting multiple variables using extract_variables
Added support for extraction of objects using extract_variables
Changes to printing behavior: (1) we do not allow a user to print variables declared in a multiverse code block from an R code block (it will throw an error); (2) we do not show the output of multiverse code blocks when knitting (as it can create hundreds or thousands of outputs)

multiverse 0.6.1

Fix for #107. Parallel execution of the multiverse (i.e. when cores >= 2 as an argument to execute_multiverse) resulted in creation of new environments and execution in these new environments, which are different from the ones that are stored in the multiverse object and returned by expand. Fixed implementation so that all the bindings from the environments were copied to the stored environments, and the resultant variable bindings can be accessed through expand (thanks, @markromanmiller, #108).
Throw errors when empty options are declared (eg. trailing commas) inside branch statements

Improved support for parallel processing using future as backend. Users can set up parallel execution workflows on both unix and non-unix systems using future. Multiverses can be executed in parallel on a local machine or concurrently on a cluster.
Support for displaying progress of execution using txtProgressBar. Use argument progress = TRUE for the function execute_multiverse().
.errors column added to the output of expand which lists the errors encountered during execution of the multiverse.
Updates to the documentation and examples, to improve walkthrough of the steps involved in creating a multiverse analysis.