boe 0.1.0

• Initial release.
• boe_get(): fetch any series by code from the BoE Statistical Database.
• boe_bank_rate(): Bank Rate history (daily or monthly, from 1975).
• boe_sonia(): SONIA interest rate (daily, monthly, or annual, from 1997).
• boe_yield_curve(): nominal and real gilt yields at 5yr, 10yr, 20yr maturities (from 1985/1993).
• boe_exchange_rate(): daily sterling exchange rates for 27 currencies (from 1975).
• list_exchange_rates(): catalogue of available currency codes.
• boe_mortgage_rates(): quoted mortgage rates (2yr/3yr/5yr fixed, SVR, from 1995).
• boe_mortgage_approvals(): monthly mortgage approvals for house purchase (from 1993).
• boe_consumer_credit(): consumer credit outstanding by type (from 1993).
• boe_money_supply(): M4 broad money amounts outstanding (from 1982).
• clear_cache(): delete locally cached data files.