Improvements for linux install

[dvdpwll]

So, I had some issues installing watchman and running ember serve, but I was able to find some resources that helped me get everything working.

I followed these instructions to get watchman installed:

$ git clone https://github.com/facebook/watchman.git
$ cd watchman
$ git checkout v4.7.0
$ sudo apt-get install -y autoconf automake build-essential python-dev
$ ./autogen.sh
$ ./configure
$ make
$ sudo make install

source: http://bravissimolabs.com/installing-watchman-on-ubuntu-14-04/
(It's similar to the official install instructions, but adds sudo apt-get instructions)
(Also I changed the versions to 4.7.0)

Next, when I tried to run ember serve I got an error about not having enough user watches:

The user limit on the total number of inotify watches was reached
increase the fs.inotify.max_user_watches sysctl

To increase the number of user watches I ran this code:

$ echo fs.inotify.max_user_watches=524288 | sudo tee -a /etc/sysctl.conf
$ sudo sysctl -p

source: https://github.com/guard/listen/wiki/Increasing-the-amount-of-inotify-watchers
(One thing the official instructions do not tell you is what the number of user watchers should be set to, or how much to increase it by. I have no idea if 524288 is way too much or what.)