Rename /data folder to clarify tutorial

[hcopperm]

In the Basecoin Basics file, it says:

Now we need some initialization files for basecoin. We have included some defaults in the basecoin directory, under data. For purposes of convenience, change to that directory:

cd $GOPATH/src/github.com/tendermint/basecoin/data
The directory contains a genesis file and two private keys.

You can generate your own private keys with tendermint gen_validator, and construct the genesis.json as you like. Note, however, that you must be careful with the chain_id field, as every transaction must contain the correct chain_id (default is test_chain_id).

1. basecoin/data should probably be renamed to basecoin/example_dir or something that is more clear
2. basecoin/data/genesis.json can be renamed to basecoin/data/bc_genesis.json
3. Docs need to be clarified here.

This issue is dependent on #48