Typo in ch12.asciidoc

Fixes #255. "The most form of unidirectional payment channel was demonstrated as a prototype" -> "The first form of unidirectional payment channel was demonstrated as a prototype"

ch12.asciidoc

@@ -283,7 +283,7 @@ Each subsequent commitment transaction must have a shorter timelock so that it m
 
 State channels use timelocks to establish smart contracts across a time dimension. In this example we saw how the time dimension guarantees that a fair commitment, representing the correct channel balance can be transmitted and confirmed before an unfair commitment transaction, representing a channel's prior state, can be transmitted and confirmed. This implementation, needs nothing more than absolute transaction level timelocks (nLockTime). Next we will see how script level timelocks, CHECKLOCKTIMEVERIFY and CHECKSEQUENCEVERIFY can be used to construct more flexible, useful, and sophisticated state channels.
 
-The most form of unidirectional payment channel was demonstrated as a prototype video streaming application in 2015 by an Argentinian team of developers. You can still see it at streamium.io.
+The first form of unidirectional payment channel was demonstrated as a prototype video streaming application in 2015 by an Argentinian team of developers. You can still see it at streamium.io.
 
 Timelocks are not the only way to invalidate prior commitment transactions. In the next sections we will see how a revocation key can be used to achieve the same result. Timelocks are effective but they have two distinct disadvantages. By establishing a maximum timelock when the channel is first opened, they limit the lifetime of the channel. Worse they force channel implementations to strike a balance between allowing long lived channels and forcing one of the participants to wait a very long time for a refund in case of premature closure. For example, if you allow the channel to remain open for 30 days, by setting the refund timelock to 30 days, if one of the parties disappears immediately the other party must wait 30 days for a refund. The more distant the endpoint, the more distant the refund. The second problem is that