Fix Illegal Seek error when reading from pipe

[copyninja]

zfec command line script now handles piping the input to it in below format.

cat some-file | zfec -

This pull request does following

• Handle when input is piped into stdin (Illegal seek error)
• Adds a basic test to check this (though we can't cleanly mock sys.stdin)
• Add setUp and tearDown functions to avoid code duplication in Cmdline test class.

Fix #3

cc: @warner @vu3rdd

[warner]

Looks good.. I'll rebase this to current master (fixing some conflicts) and land momentarily.