Update requirement expectations

Based on a node I just setup.
Merge pull request #124 from drak/patch-1

Update requirement expectations
Update README.md

remove references to the upgrade script.
add startAt opts in sync
Merge pull request #126 from matiu/feature/startAt

add startAt opts in sync
fix error in scriptpubkey cache
add test for backwars compat
Merge pull request #127 from matiu/bug/cache01

Bug/cache01
0.2.7
ignore /public in npm
ignore /public in npm / git
Merge pull request #128 from matiu/feature/v0.2.7

Feature/v0.2.7