add downloader to pull node's buffer tests
download node's buffer tests
update from-string tests and rename from utf16
mimic SlowBuffer and Buffer#parent just enough to pass node's tests
fix broken max-length check
update bounds checks and throw RangeErrors instead of TypeErrors for failures
copy should return length
base64 changes to improve node compatibility
add generic functions for (u)int ops - copied from node commit 83d7d9e
make generic (u)int ops work when TYPED_ARRAY_SUPPORT is false
strip high bit when ascii slicing
do not encode partial code units to utf16
add benchmark for encoding to utf8
do not encode partial or invalid code points to utf8