fix Mac OS and Windows build instructions grammar

doc/How to build - Mac OS.md

@@ -18,12 +18,12 @@ This will create a dependencies bundle inside the `build/destdir` directory.
 You can also customize the bundle output path using the `-DDESTDIR=<some path>` option passed to `cmake`.
 
 **Warning**: Once the dependency bundle is installed in a destdir, the destdir cannot be moved elsewhere.
-(This is because wxWidgets hardcode the installation path.)
+(This is because wxWidgets hardcodes the installation path.)
 
 
 ### Building Slic3r
 
-If dependencies built without an error, you can proceed to build Slic3r itself.
+If dependencies are built without errors, you can proceed to build Slic3r itself.
 Go back to top level Slic3r sources directory and use these commands:
 
     mkdir build

doc/How to build - Windows.md

@@ -7,7 +7,7 @@ CMake installer can be downloaded from [the official website](https://cmake.org/
 
 Building with newer versions of MSVS (2015, 2017) may work too as reported by some of our users.
 
-_Note:_ Thanks to [**@supermerill**](https://github.com/supermerill) for testing and inspiration on this guide.
+_Note:_ Thanks to [**@supermerill**](https://github.com/supermerill) for testing and inspiration for this guide.
 
 ### Dependencies
 
@@ -20,7 +20,7 @@ The package comes in a several variants:
   - [32 bit, Release mode only](https://bintray.com/vojtechkral/Slic3r-PE/download_file?file_path=destdir-32.7z) (38 MB, 520 MB unpacked)
   - [32 bit, Release and Debug mode](https://bintray.com/vojtechkral/Slic3r-PE/download_file?file_path=destdir-32-dev.7z) (74 MB, 1.1 GB unpacked)
 
-When unsure, use the _Release mode only_ variant, the _Release and Debug_ variant is only needed for debugging & developement.
+When unsure, use the _Release mode only_ variant, the _Release and Debug_ variant is only needed for debugging & development.
 
 If you're unsure where to unpack the package, unpack it into `C:\local\` (but it can really be anywhere).
 
@@ -46,13 +46,13 @@ Conversely, if you're using Visual Studio version other than 2013, the version n
 
 If `cmake` has finished without errors, go to the build directory and open the `Slic3r.sln` solution file in Visual Studio.
 Before building, make sure you're building the right project (use one of those starting with `slic3r_app_...`) and that you're building
-with the right configuration, ie. _Release_ vs. _Debug_. When unsure, choose _Release_.
+with the right configuration, i.e. _Release_ vs. _Debug_. When unsure, choose _Release_.
 Note that you won't be able to build a _Debug_ variant against a _Release_-only dependencies package.
 
 #### Installing using the `INSTALL` project
 
 Slic3r PE can be run from the Visual Studio or from Visual Studio's build directory (`src\Release` or `src\Debug`),
-but for longer-term usage you migth want to install somewhere using the `INSTALL` project.
+but for longer-term usage you might want to install somewhere using the `INSTALL` project.
 By default, this installs into `C:\Program Files\Slic3r`.
 To customize the install path, use the `-DCMAKE_INSTALL_PREFIX=<path of your choice>` when invoking `cmake`.
 
@@ -91,7 +91,7 @@ You can also use the Visual Studio GUI or other generators as mentioned above.
 The `DESTDIR` option is the location where the bundle will be installed.
 This may be customized. If you leave it empty, the `DESTDIR` will be places inside the same `build` directory.
 
-Note that the build variant that you may choose using Visual Studio (ie. _Release_ or _Debug_ etc.) when building the dependency package is **not relevant**.
+Note that the build variant that you may choose using Visual Studio (i.e. _Release_ or _Debug_ etc.) when building the dependency package is **not relevant**.
 The dependency build will by default build _both_ the _Release_ and _Debug_ variants regardless of what you choose in Visual Studio.
 You can disable building of the debug variant by passing the `-DDEP_DEBUG=OFF` option to CMake, this will only produce a _Release_ build.