Add pythainlp.g2p.ipa

[wannaphong]

• Add Thai to IPA by epitran

from pythainlp.g2p import ipa
t=ipa("คน")
t.str() #'kʰon'
t.list() # ['kʰ', 'o', 'n']
t.xsampa_list() # ['k_h', 'o', 'n']

[coveralls]

Coverage increased (+0.3%) to 58.061% when pulling 606528e on g2p into c148699 on dev.

[coveralls]

Coverage increased (+0.3%) to 58.061% when pulling 606528e on g2p into c148699 on dev.

[coveralls]

Coverage increased (+0.3%) to 58.061% when pulling 606528e on g2p into c148699 on dev.

[bact]

Enhancement #116