Fixed running examples.

For some reason, examples have a colon after "RUN".

```
go test -v
=== RUN TestXOR
--- PASS: TestXOR (0.00 seconds)
=== RUN TestCBCEncrypterAES
--- PASS: TestCBCEncrypterAES (0.00 seconds)
=== RUN TestCBCDecrypterAES
--- PASS: TestCBCDecrypterAES (0.00 seconds)
=== RUN TestCFB
--- PASS: TestCFB (0.00 seconds)
=== RUN TestCryptBlocks
--- PASS: TestCryptBlocks (0.00 seconds)
=== RUN TestCTR_AES
--- PASS: TestCTR_AES (0.00 seconds)
=== RUN TestAESGCM
--- PASS: TestAESGCM (0.00 seconds)
=== RUN TestOFB
--- PASS: TestOFB (0.00 seconds)
=== RUN: ExampleNewCBCDecrypter
--- PASS: ExampleNewCBCDecrypter (9.93us)
=== RUN: ExampleNewCFBDecrypter
--- PASS: ExampleNewCFBDecrypter (7.411us)
=== RUN: ExampleNewCTR
--- PASS: ExampleNewCTR (11.72us)
=== RUN: ExampleNewOFB
--- PASS: ExampleNewOFB (16.021us)
PASS
ok  	github.com/qpingu/crypto/cipher	0.003s
```