updated path to build pack binaries on S3
only need to vendor R directory since packages cannot be installed once the slug is compiled
improvements to build script for clean up of unneeded files
revert updated path to build pack binaries on S3
optimize slug size by removing unneeded files after compilation
updated read me
only copy known directories
create blank file to prevent R compiler warnings for documentation
copy gfortran libs to R libs folder to simplify library resolutions
export the BUILD_DIR variable so that `init.r` can pick it up for locally sourced packages
want R outputs while executing `init.r`
exporting BUILD_DIR didn't work, so set the working directory explicitly in the R code
updated readme
updated init.r as per suggestion by @chahu
Merge pull request #12 from virtualstaticvoid/development

Incorporate enhancements from development branch