[packrat] removing src/ folder

packrat/src/BH/BH_1.72.0-3.tar.gz

packrat/src/DT/DT_0.16.tar.gz

packrat/src/R6/R6_2.5.0.tar.gz

packrat/src/RCurl/RCurl_1.98-1.2.tar.gz

packrat/src/Rcpp/Rcpp_1.0.5.tar.gz

packrat/src/XML/XML_3.99-0.5.tar.gz

packrat/src/askpass/askpass_1.1.tar.gz

packrat/src/assertthat/assertthat_0.2.1.tar.gz

packrat/src/base64enc/base64enc_0.1-3.tar.gz

packrat/src/bitops/bitops_1.0-6.tar.gz

packrat/src/brew/brew_1.0-6.tar.gz

packrat/src/brio/brio_1.1.0.tar.gz

packrat/src/callr/callr_3.5.1.tar.gz

packrat/src/cli/cli_2.2.0.tar.gz

packrat/src/clipr/clipr_0.7.1.tar.gz

packrat/src/commonmark/commonmark_1.7.tar.gz

packrat/src/covr/covr_3.5.1.tar.gz

packrat/src/cpp11/cpp11_0.2.4.tar.gz

packrat/src/crayon/crayon_1.3.4.tar.gz

packrat/src/crosstalk/crosstalk_1.1.0.1.tar.gz