Making the validation of identifier names match the spec and docs
Making the validation of identifier names match the spec and docs

Underscores weren't being allowed when the should have been.
https://github.com/neumino/reqlite/issues/25

Test:

```
nesh*> yield r.dbCreate('al_stewart')
{ config_changes: [ { new_val: [Object], old_val: null } ],
  dbs_created: 1 }
nesh*> yield r.dbList()
[ 'al_stewart' ]
```

AusIV/reqlite,neumino/reqlite,neumino/reqlite