Hardcode version, add a release script

[motiejus]

Having thought about this more, I am semi-reverting fcd4d58c5532001b6ae2e28555318818c06e79ca in favor of hardcoding the version to the binary and a release script.

[motiejus@mtworx:~/code/btrfs-auto-snapshot]$ ./release v3.0.0
+ sed -i s/^\(BTRFS_AUTO_SNAPSHOT_VERSION\)=.*/\1=v3.0.0/ btrfs-auto-snapshot
+ git add btrfs-auto-snapshot                           
+ git commit -m btrfs-auto-snapshot v3.0.0                                
[release-script 27c55c5] btrfs-auto-snapshot v3.0.0
1 file changed, 1 insertion(+), 1 deletion(-)
+ git tag v3.0.0
+ sed -i s/^\(BTRFS_AUTO_SNAPSHOT_VERSION\)=.*/\1=v3.0.0+dev/ btrfs-auto-snapshot
+ git add btrfs-auto-snapshot           
+ git commit -m "btrfs-auto-snapshot v3.0.0+dev"                   
[release-script 4598c6e] btrfs-auto-snapshot v3.0.0+dev
 1 file changed, 1 insertion(+), 1 deletion(-)                                                                                                       

You have tagged v3.0.0. Now run the following:
  git push origin master                 
  git push origin v3.0.0

[motiejus]

@hunleyd I accidentally pushed this to your branch release-script instead of mine, but cannot delete the branch. Sorry.