Merge pull request #7 from lukechampine/papers

more spellchecking/rewording
add section for intro, proof of storage, proof of transfer
addressing.txt will be the new whitepaper
flesh out an introduction to Sia
add section on consensus
talk about lightweight blockchain
attempt to explain proof of capacity
add simulation for proof of capacity
rename sim filenames
further flesh out proof of capacity
new introduction
update building block sections
start explaining quorums
outline an overview
finish overview of architecture
added an appendix, moved stuff there
add bibliography
explain bgp for single quorums
framework for remaining single quroum discussion
talk about timing and block progression