Typo in regexp-en.png file

[yuhwan]

The second square closing brace should be the curly brace to represent quantifiers properly. So, the regex should be ^[a-z0-9_-]{3,15}$ rather than ^[a-z0-9_-]{3,15]$.

[ponsfrilus]

Thank, just seen that. See 5e40ce0

[ponsfrilus]

Fixed in #77