create_roles.sql inconsistant with instal instructions

[Window-Hero]

The install instructions provided in the main README instruct the user to create a postgres user "selene", set a password, and set an environmental variable to match the password used, however the bootstrap_mycroft_db.py script refers to create_roles.sql and overwrites this password with a predefined default "adam", but then when the bootstrap script attempts to log in as the selene user it tries to use the password defined in the environmental variable, which is no longer correct, since it has been overwritten.

To replicate: Follow the instructions in the README, attempt to run the bootstrap_mycroft_db.py script after having defined a selene user and an environmental variable for the password, the script will fail to authenticate as selene.

Proposed fixes: Under the current instructions create_roles.sql is entirely unnecessary, because all it does is overwrite the user that was already created. Either the usage of this file could be eliminated, or the file could be modified to use the password the user provides in the environmental variable.