Support filter transactions by amount

[ranmocy]

Usage:

# Get only credit transactions
mm.get_transactions(is_credit: True)

# Get only debit transactions
mm.get_transactions(is_credit: False)

# Get whose amount is >= 4.2
mm.get_transactions(abs_amount_range: [4.2, None])

# Get whose amount is <= 4.2
mm.get_transactions(abs_amount_range: [None, 4.2])

# Get whose amount is == 4.2
mm.get_transactions(abs_amount_range: [4.2, 4.2])

# Get whose amount is between 2.1 and 4.2
mm.get_transactions(abs_amount_range: [2.1, 4.2])