Use reference to alphabet instead of '1'.

Line 34 replaces leading zeros with ```alphabet[0]``` so line 60 should perform the inverse operation. This is only an issue if alphabet is modified.
Merge pull request #3 from deckar01/fix-prefix-value

Use alphabet[0] instead of '1'.
refactor a bit
remove binstring dep
small case refactorings
change description
added fixtures file from bitcoinjs-lib
update to latest bigi
update fixtures, tests
add travis-ci support
readme update
ignore coverage
modify more for coveralls support
1.0.0
Update CHANGELOG.md
proper attribution