add monospaced font

[tuchengpanghu]

• using DejaVu Sans Mono so characters like a and l are in the same width
• adjusted title width when title is in Chinese
• adjusted title padding(left and right)

[tuchengpanghu]

• before
• after

[tuchengpanghu]

downloaded latest DejaVuSansMono from here.

[tuchengpanghu]

• before when showing Chinese characters
• after