Some suggested grammar improvements (happi#23)

Grammar fixes.

introduction.asciidoc

@@ -54,7 +54,7 @@ xref:P-ERTS[] of this book you will get a deep understanding of
 how the runtime system works.
 
 In the following chapters of xref:P-ERTS[] I will try to explain each
-component of the system by itself, in one separate chapter for each of
+component of the system by itself, in a separate chapter for each of
 the major component. You should be able to read any one of these
 chapters without having a full understanding of how the other
 components are implemented, but you will need a basic understanding of
@@ -98,7 +98,7 @@ the _ERTS Stack_.
 In xref:the_erts_stack[] you can see the ERTS Stack illustrated with
 two Erlang nodes running on one machine.
 
-In the bottom of the stack there is the hardware you are running
+At the bottom of the stack there is the hardware you are running
 on. The easiest way to improve the performance of your app is probably
 to run it on better hardware. If economical or physical constraints
 won't let you upgrade your hardware you can start exploring higher
@@ -116,8 +116,8 @@ versions of Windows and most POSIX "compliant" OS:es, including Linux,
 VxWorks, Solaris, and Mac OS X. Today most of the development of ERTS
 is done on Linux and OS X, and you can expect the best performance on
 these platforms. However, Ericsson have been using Solaris internally
-in many projects and ERTS have been tuned for Solaris for many years.
-Depending on your use case you might actually get best performance on
+in many projects and ERTS has been tuned for Solaris for many years.
+Depending on your use case you might actually get better performance on
 a Solaris system. The OS choice is usually not based on performance
 requirements, but is restricted by other demands. If you are building
 an embedded application you might be restricted to Raspbian or VxWorks,