add service LYModel

this service provides a simple cache.
for a http get request, it checks whether the request is already
exists in cache and return it.

Otherwise, it uses $http to execute the request and stores reponse
into cache before return to caller.
sittings: use LYModel
add git version note in README
calendar:onair is broken, because "time" is empty. check and use time_start and time_end instead if time is null
use diff_match_patch from cdnjs
cleanup
fix delete & insert em problem
cleanup
minor LS style tweaks
add avatar on hover; wrap clip and waveform; refactor ngwaveform; adjust svg+waveform margin
Merge branch 'master' of github.com:g0v/ly.g0v.tw
add date info in waveforms
Fix diff bugs

 * Fix bad state in /bills/1037L15522
 * improve semantic for /bills/1011130070300200

Closed #42
with diff_match_patch, we don't need basetext hack anymore
Don't fail on youtube api failure
show article heading in compact number with zhutil
regen for 96c0483