use new extension in examples and benchmarks as well
fix batch mode

in some (most?) cases it didn't read multiple expressions, although it
did read and execute the two print expressions from the previous hello
world example.

doing it this way has the advantage of executing the statements as they
are read.
split load-file into load-ns and load-file

load-file now just loads and runs a file at the given path, while
load-ns searches for a file relative to load-paths.
add load-reader
use load-reader in batch mode
Merge pull request #74 from heyLu/fix-batch-mode

Fix batch mode