Update note about old libsolc API

Author: r0qs

README.md

@@ -205,7 +205,9 @@ The low-level API is as follows:
 For examples how to use them, please refer to the README of the above mentioned solc-js releases.
 
 **Note**: These low-level functions remain available for compatibility reasons.
-However, they were superseded by the `compile()` function and are no longer required in newer versions. The functions `compileSingle`, `compileMulti` and `compileCallback` are always `null` in the newer versions.
+However, they were superseded by the `compile()` function and are no longer required.
+Starting in version `0.5.0+commit.1d4f565a`, the functions `compileSingle`, `compileMulti`, and `compileCallback` are always `null` when using newer binary versions.
+It is recommended to use the latest release of solc-js, but it should also handle all the older binaries down to `0.1.x`.
 
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