Updates documentation to 0.7.0.

docs/contracts/libraries.rst

@@ -47,7 +47,7 @@ more advanced example to implement a set).
 
 ::
 
-    pragma solidity >=0.4.22 <0.7.0;
+    pragma solidity >=0.4.22 <0.8.0;
 
 
     // We define a new struct datatype that will be used to
@@ -123,7 +123,7 @@ custom types without the overhead of external function calls:
 
 ::
 
-    pragma solidity >=0.4.16 <0.7.0;
+    pragma solidity >=0.4.16 <0.8.0;
 
     struct bigint {
         uint[] limbs;
@@ -237,7 +237,7 @@ Its value can be obtained from Solidity using the ``.selector`` member as follow
 
 ::
 
-    pragma solidity >0.5.13 <0.7.0;
+    pragma solidity >0.5.13 <0.8.0;
 
     library L {
         function f(uint256) external {}