replace SCRIPT_VERSION by git describe
move processing of messages to context

note that msg_convert_in calls utf8_decode first, whereas the code
previously called utf8_decode after processing which could lead to
problems depending on the type of processing done.
add filter for incoming html

adds a htmlparser class that will filter any html but newlines and links
(kept in markdown-like syntax) and converts html-entities to unicode.
add incoming message HTML filter policy

if this policy is on (default), html tags are stripped from incoming
messages. this is useful if your peer uses a graphical client that sends
html formatted messages over otr.

you can turn this off per-peer.
add testcase for IrcHTMLParser
Merge pull request #59 from tribut/git-version

replace SCRIPT_VERSION by git describe
Move git describe into method.

Use --git-dir instead of chdir.
Ignore OSError in case git is not installed.
Add allow failure python 3.3 build to Travis.
Merge pull request #60 from tribut/filter-html

Filter incoming html
Make excepts python 3 compatible.
Use python 3 octal literal syntax.
Use io instead of cStringIO.