Added body function

The body function can be thought of as printing the first line of input and piping the rest to a process.  Examples:

1. sort a CSV with a header:
> cat in.csv | body sort -k1 > out.csv

2. Print first line and all lines after than with hello:
> cat in.txt | body grep 'hello'

References:
http://unix.stackexchange.com/questions/11856/sort-but-keep-header-line-in-the-at-the-top