Update book links to gitbook

CONTRIBUTING.md

@@ -103,7 +103,7 @@ Solana's architecture is described by a book generated from markdown files in
 the `book/src/` directory, maintained by an *editor* (currently @garious). To
 add a design proposal, you'll need to at least propose a change the content
 under the [Accepted Design
-Proposals](https://solana-labs.github.io/book-edge/proposals.html) chapter.
+Proposals](https://docs.solana.com/book/v/master/proposals) chapter.
 Here's the full process:
 
 1. Propose a design by creating a PR that adds a markdown document to the

README.md

@@ -26,9 +26,9 @@ Furthermore, and much to our surprise, it can be implemented using a mechanism t
 Architecture
 ===
 
-Before you jump into the code, review the online book [Solana: Blockchain Rebuilt for Scale](https://solana-labs.github.io/book/).
+Before you jump into the code, review the online book [Solana: Blockchain Rebuilt for Scale](https://docs.solana.com/book/).
 
-(The _latest_ development version of the online book is also [available here](https://solana-labs.github.io/book-edge/).)
+(The _latest_ development version of the online book is also [available here](https://docs.solana.com/book/v/master/).)
 
 Release Binaries
 ===
@@ -120,7 +120,7 @@ $ cargo test
 Local Testnet
 ---
 
-Start your own testnet locally, instructions are in the book [Solana: Blockchain Rebuild for Scale: Getting Started](https://solana-labs.github.io/book/getting-started.html).
+Start your own testnet locally, instructions are in the book [Solana: Blockchain Rebuild for Scale: Getting Started](https://docs.solana.com/book/getting-started).
 
 Remote Testnets
 ---

programs/btc_spv_api/README.md

@@ -61,4 +61,4 @@ Client Request - Transaction from the client to the SPV Program to trigger creat
 Sub-account - A Solana account owned by another contract account, without its own private key.
 
 For more information on the Inter-chain SPV system, see the book section at:
-https://solana-labs.github.io/book/interchain-transaction-verification.html
+https://docs.solana.com/book/v/master/proposals/interchain-transaction-verification