Fix hand wiring guide (#387)

* Fix broken link

* Fix incoherent sentence

doc/HAND_WIRE.md

@@ -195,7 +195,7 @@ You'll want to navigate to the `keyboard/<project_name>/` folder by typing, like
 
 #### config.h
 
-The first thing you're going to want to modify is the `config.h` file. Find `MATRIX_ROWS` and `MATRIX_COLS` and them to match the dimensions of your keyboard's matrix.
+The first thing you're going to want to modify is the `config.h` file. Find `MATRIX_ROWS` and `MATRIX_COLS` and change their definitions to match the dimensions of your keyboard's matrix.
 
 Farther down are `MATRIX_ROW_PINS` and `MATRIX_COL_PINS`. Change their definitions to match how you wired up your matrix (looking from the top of the keyboard, the rows run top-to-bottom and the columns run left-to-right). Likewise, change the definition of `UNUSED_PINS` to match the pins you did not use (this will save power).
 
@@ -282,7 +282,7 @@ It's also important to use the `KEYMAP` function we defined earlier - this is wh
 
 #### Compiling your firmware
 
-After you've written out your entire keymap, you're ready to get the firmware compiled and onto your Teensy. Before compiling, you'll need to get your [development environment set-up](https://github.com/jackhumbert/qmk_firmware/blob/master/keyboard/planck/PCB_GUIDE.md#setting-up-the-environment) - you can skip the dfu-programmer instructions, but you'll need to download and install the [Teensy Loader](https://www.pjrc.com/teensy/loader.html) to get the firmware on your Teensy.
+After you've written out your entire keymap, you're ready to get the firmware compiled and onto your Teensy. Before compiling, you'll need to get your [development environment set-up](./BUILD_GUIDE.md) - you can skip the dfu-programmer instructions, but you'll need to download and install the [Teensy Loader](https://www.pjrc.com/teensy/loader.html) to get the firmware on your Teensy.
 
 Once everything is installed, running `make` in the terminal should get you some output, and eventually a `<project_name>.hex` file in that folder. If you're having trouble with this step, see the end of the guide for the trouble-shooting section.