StakeModifierCheckpoints in Params
travis.yml: no -u
test: use first 6504 ppc blocks
test: use correct file
ppc: compatibility w/ new btcnet.Params (CoinbaseMaturisy, StakeMinAge, ModifierInterval)
GetProofOfWorkReward implementation
kernel.go: fix candidates sorting
Squashed commit of the following:

commit 86b84e6d9bde7f30734f798684d5ba02b070d28b
Author: mably <f.mably@gmail.com>
Date:   Thu Sep 18 10:31:37 2014 +0200

    vSortedByTimestamp with equal block time fix, sort by hash added

commit e01995edcd2fe078020daa2b96f203c57476f69d
Author: kac- <6b6163@gmail.com>
Date:   Wed Sep 17 21:50:08 2014 +0200

    kernel.go: added hash comparison to blockTimeHashSorter for candidates

commit 31ffbcd18bcafd0f3b0b7854327294d43027d538
Author: kac- <6b6163@gmail.com>
Date:   Wed Sep 17 20:03:48 2014 +0200

    make this test pass
Removed useless ChainTrust code
No fees to reward miners in ppcoin
Mint and money supply calculations
GetCoinAge methods
ppc: few fixes and checks
ppc: enforce transaction fees for every block
ppc: checks: wrong coinstake position
ppc: checks: empty coinbase output and coinstake timestamp
ppc: checks: block timestamp and signature
ppc: limited stake duplicity check
Merge pull request #4 from mably/topic/checks_rebase

ppc specific checks
Merge branch 'master' into topic/fastadd