v0.2.13

Changes:

• Removed the dependency on XML. This will only affect a non-essential function (getCranDesription) on versions of R prior to R-3.4.0

Bug fixes:

• Fix "t undefined in scope error" #125, contributed by @calligross (https://github.com/calligross)
• Update code and tests to write PACKAGES.rds with compression version 2 for versions of R earlier than R-3.5.0 #129

Minor changes:

• Removed reference to dependency on curl, since the actual dependency was removed in a previous version of the package.
• Treat the writePACKAGES argument consistently, as suggested by @vh-d in #130
• Improve test coverage
• Fix some broken examples