Adding sjcl

Should we bundle a minified sjcl bundle or convert each component to AMD (that might take time)? 


SJCL Bundle Built with:
```
~/mozilla/sjcl on master*
$ ./configure --with-convenience
Enabled components:
  aes
  bitArray
  codecString
  codecHex
  codecBase64
  sha256
  ccm
  ocb2
  gcm
  hmac
  pbkdf2
  random
  convenience
  
Compression: closure
~/mozilla/sjcl on master*
$ make
cat core/sjcl.js core/aes.js core/bitArray.js core/codecString.js core/codecHex.js core/codecBase64.js core/sha256.js core/ccm.js core/ocb2.js core/gcm.js core/hmac.js core/pbkdf2.js core/random.js core/convenience.js  > core.js
compress/compress_with_closure.sh core.js > core_closure.js
cp core_closure.js sjcl.js
```

Currently:
```
build/gherkin.js
Size:		57.64 Kb
Gzip Size:	18.18 Kb

build/gherkin.min.js
Size:		34.75 Kb
Gzip Size:	12.75 Kb
```