elementary code style

[cjfloss]

Fix warnings from vala-linter

[megatux]

I'm not a reviewer, but looks ok to me :)

[ryonakano]

The latest vala-lint suggests the following message:

src/Tomato.vala
   35.5     error   Expected variable name in ALL_CAPS_CONVENTION   naming-convention

This is the applicable line:

tomato/src/Tomato.vala

Line 35 in 1e54514

protected const string[] break_messages = {N_("Go have a coffee"),

Diff:

-protected const string[] break_messages = {N_("Go have a coffee"),
+protected const string[] BREAK_MESSAGES = {N_("Go have a coffee"),