Minor updates to the README (decred#75)

Make it clearer that atomic swaps may be performed through any two
supported coins, instead of only being Decred compatible.

Remove the build dependency on dcrwallet 1.1.0.  This was actually
never a build dependency, but a runtime dependency, and any older
Decred releases have been forked off the network due the activation of
the lnfeatures agenda via consensus vote.

README.md

@@ -3,14 +3,15 @@ secret sizes to prevent fraudulent swaps between two cryptocurrencies with
 different maximum data sizes.  Old contracts will not be usable by the new tools
 and vice-versa.  Please rebuild all tools before conducting new atomic swaps.
 
-# Decred cross-chain atomic swapping
+# Decred-compatible cross-chain atomic swapping
 
-This repo contains utilities to manually perform cross-chain atomic swaps
-between Decred and other cryptocurrencies.  At the moment, support exists for
-the following coins and wallets:
+This repository contains utilities to manually perform cross-chain atomic swaps
+between various supported pairs of cryptocurrencies.  At the moment, support
+exists for the following coins and wallets:
 
 * Bitcoin ([Bitcoin Core](https://github.com/bitcoin/bitcoin))
 * Bitcoin Cash ([Bitcoin ABC](https://github.com/Bitcoin-ABC/bitcoin-abc), [Bitcoin Unlimited](https://github.com/BitcoinUnlimited/BitcoinUnlimited), [Bitcoin XT](https://github.com/bitcoinxt/bitcoinxt))
+* Decred ([dcrwallet](https://github.com/decred/dcrwallet))
 * Litecoin ([Litecoin Core](https://github.com/litecoin-project/litecoin))
 * Monacoin ([Monacoin Core](https://github.com/monacoinproject/monacoin))
 * Particl ([Particl Core](https://github.com/particl/particl-core))
@@ -22,7 +23,8 @@ the following coins and wallets:
 Pull requests implementing support for additional cryptocurrencies and wallets
 are encouraged.  See [GitHub project
 1](https://github.com/decred/atomicswap/projects/1) for the status of coins
-being considered.
+being considered.  Implementing support for a new cryptocurrency provides atomic
+swap compatibility between all current and future supported coins.
 
 These tools do not operate solely on-chain.  A side-channel is required between
 each party performing the swap in order to exchange additional data.  This
@@ -43,7 +45,6 @@ Pre-requirements:
 
   - Go 1.9 or later
   - [dep](https://github.com/golang/dep)
-  - `dcrwallet` 1.1.0 or later (for `dcratomicswap`)
 
 ```
 $ cd $GOPATH/src/github.com/decred