[misc] Fix typo
[build][mbed] Define `XI_USER_AGENT`
[build][mbed] Get version from a header
[temp] Script to push to mercurial (should be a make target)
[build] Add make target to push to mbed.org repo
[clean] Remove old zip file helper
[build] Point to correct upstream repo
[fix] Silly copypasta
[fix] ARM's CPP doesn't seem to like this -

Perhaps there is a way of doing this, but it's not 100% necessary.
[fix][mbed] Include protable header `TCPSocketConnection.h`
[feature] Allow users to override constants with config header (close #51)
[feature] The user config is required -

As discussed in #51, it is best to keep this header optional
and only require it in mbed online IDE as user has no control
over compiler flags and/or global constats etc.
[misc] A more appropriate name for config header
[feature] More user config options -

These headers rely on various macros which users should be able to
override via `xi_user_config.h` which we now allow (#51).