Change filename length restriction to 60 characters & word truncation

Example of a longer filename:
- 3e12cdb9209d_alter_user_table_telephone_and_mobile_columns.py

Example of a filename that has been truncated:
- 12894284029g_create_partial_index_for_article_telephone_column_and_.py
Merged in Frozenball/alembic/longer-filenames (pull request #12)

Change filename length restriction to 60 characters & word truncation