Several improvments and bugfixes

0. Support the pay-to-pubkey script
1. Support address list instead of a single address for parameter --cbaddr, multiple addresses are separated by ',' or '+'
2. Remove the '<' and '=" comparison, since what we really want is just '>=', so that we can simply the code a little bit
3. Convert the caculated percentage to float to avoid annoying precision problem during comparing;
4. Others...

Signed-off-by: Huang Le <4tarhl@gmail.com>
Add the ripemd160 algorithm which was needed to support pay-to-pubkey script

Signed-off-by: Huang Le <4tarhl@gmail.com>