Minor text fix for mainpage.md

Rearranged sentence so that only one 'and' is used in the sentence

doc/doxygen/src/mainpage.md

@@ -8,9 +8,9 @@ RIOT in a nutshell {#riot-in-a-nutshell}
 RIOT is an open-source microkernel-based operating system, designed to match
 the requirements of Internet of Things (IoT) devices and other embedded
 devices. These requirements include a very low memory footprint (on the order
-of a few kilobytes), high energy efficiency, real-time capabilities,
-communication stacks for both wireless and wired networks, and support for a
-wide range of low-power hardware.
+of a few kilobytes), high energy efficiency, real-time capabilities,support for a
+wide range of low-power hardware, communication stacks for wireless and 
+communication stacks for wired networks.
 
 RIOT provides a microkernel, multiple network stacks, and utilities which
 include cryptographic libraries, data structures (bloom filters, hash tables,
@@ -111,7 +111,7 @@ core
 ----
 This directory contains the actual kernel. The kernel consists of the
 scheduler, inter-process-communication (messaging), threading, thread
-synchronization, and supporting data-structures and type definitions.
+synchronization, supporting data-structures and type definitions.
 
 See @ref core for further information and API documentations.