Added "simplified variant" field into table.txt

The current table.txt provides no data for the "type traditional
output simplified" features.

This commit added a new field of "simplified variant" data into
table.txt so db_builder can build data on. Which provides building
block for the "type traditional output simplified" feature.

For puncutuations and non-Chinese characters, there is no "simplified
variant" and hence an "NA" there.

Please note that this commit will break builds. The following
commit(s) will fix build by adpoting this change into db_builder.
Modify dbbuilder to fit the new table.txt format

Added the simpchar field into database. Updated the dbbuilder so it
will parse and insert the "simplified variant" field data into the
database.
Remade README.table.rst to README.table.md

All other README and documentations in this project is in markdown
format. It make sense to change this file to markdown too. Also
removed all number words from the file to make it easier to change.

To adapt the changed filename, also changed the references in
Makefile.am and table.txt
Added documentation line for the new table.txt field

Added the description for the new "Simplified Chinese equivlant character"
field. Also provided example.
Added simpchar to cangjiechar (API break)

This commit added "simplified variant" field result into a new
struct field simpchar in cangjiechar. SQL queries are updated to
query and pass the data correctly.
Updated CLI to output the new simpchar field

Updated CLI to output the new simplified variant field. Users may
examine the results with CLI.

Also wrap character output and simplified character output with "'"
to make it looks better (especially the simplified character field).
Modify unit test for the new API change

Modified the cangjie_char_new() statments to add simpchar.
Also added the assertion of simpchar field.

Should fix the error in Travis CI building process.

Changes from ee038be to this commit should be sufficient to
resolve #40.
Update documentations to the changed API

The function cangjie_char_new() and the struct CangjieChar have
been changed. This commit updated the relevant documentations for
these changes.