cmd: introduce rowList type to table

This type will represent a list of tables. This list will be sortable.

Related to #345.
cmd: make rowList sortable

Related to #345.
cmd: use rowList to represent rows in Table

Related to #345.
cmd: added Sort method to Table type

This method will sort rows in the table using the first column of each
row as the key for sorting. This is just how rowList works.

Related to #345.
cmd: using case insensitive sort in the table

Related to #345.
cmd/tsuru-base: sort apps in app-list output

Closes #345.
cmd: display targets in alphabetical order
cmd: remove unnecessary call to Fprintf