Add needed dependencies for compilation

[Jiehong]

Hi,

It would be nice to add a word in the readme file about what dependencies are required. For example, on Ubuntu/Debian, you need the following 2 packages:

pidgin-dev >= 2.4.0
libpurple-dev >= 2.4.0

Cheers

[Jiehong]

as a matter of fact, I cannot build it with the following error afterwards:

main.h:55:24: fatal error: curl/types.h: No such file or directory
 #include <curl/types.h>

Yet, during ./configure, I get the following:

checking for curl-config... /usr/bin/curl-config
checking for the version of libcurl... 7.35.0
checking for libcurl >= version 7.19.1... yes
checking whether libcurl is usable... yes
checking for curl_free... yes

Any idea what's going on here?

[Jiehong]

Note, this is on Ubuntu 14.04 LTS.